Same reason Family Guy and every Tv show and movie do it.
[Lots of Legal Explanation without Legal Terms]
I am not a lawyer, but I have had some experience. Feel free to ask me for details if needed, and I'll pull up the legal documentation for this stuff.
Basically, In the big bad world of grown-ups and companies, there is this concept of credit and ownership. If I make a company (which I am actually), there are things I can own. I can own the name of my company, I can trademark thins like the logo to say that it then is owned by my company (which acts as a separate taxable entity). Ownership is ownership. You own your computer, your data, your body, and a company owns its name. Following the laws of ownership, no one but you is legally allowed to use your computer, your data, your body, etc. without your consent. The same thing applies to company names, you are not technically allowed to use the works of others. Fan fictions, for example, is a gray area since no supreme court rulings go for or against this form of transformative work specifically. Star wars based porn games are a community favorite but always a worry that it could be stricken down based on that such a work may infringe upon copyright ownership, the best people can do is add a disclaimer letting people know it is not actually related to Star Wars in real life.
What's the worst that could happen? best case and most of the time, no one notices and your project stays ok. Or the best of a bad situation, your game is banned or removed. Very rare but it happens a lot with youtube videos. Nintendo is infamous for having a strike copyright policy, because it is currently owned by a bunch of old dead dumb asses who haven't adapted to the current standards of the modern era and still practice the age-old tradition of squeezing the system of every Nickle and penny they can get their hands on. Worst case, that company wants to sue you for what is called "copyright infringement." In the adult world, there are 4 things out there, money, material property, Intelectual Property (often called IP for short), and ideas. You can not own an idea, but you can own an object. Intellectual Property is in between, it is an idea "given form." Once you make or design something then we are willing to say you own that idea. For example, the company I am trying to make, I am in the first phase of making contracts and agreements, where the only thing that matters is that my coworkers understand that all of their work, their paperwork or powerpoints they make, belong to me and my company and not them. If I didn't do this then there is the danger that they could claim ownership of part of my company, demand money, and legally be able to walk away from my company and take a lot of it with them. Copyright is the form of ownership for IPs and in the business world it is a very serious concern.
Now there are a few exceptions to this. Personal/Non-Commercial Usage, Public Domain, Transformative Work/Fair Use,Licenses or Paid Promotion. Suing based on Copyright infringement is based on the concept that you own 'something' with the intent of making money off of said 'thing'. So it can be hard to sue someone who isn't making a profit if you have to somehow argue in court that said person is somehow damaging your ability to make money or stealing money that should have gone to the IP owner. So things you make for your self don't have this problem. Things you share for free with a non-commercial licence usually don't have this problem. Anything that belongs to the Public Domain, means it is free for anyone to use. This can be because someone who owns something releases it into the public domain, like a free video game asset, or it could be that the IP ownership has expired, such as with the Wizard of Oz book is over a century old and the author no longer owns the IP, It was released to the public domain a few years ago, so you can make a porn game set in the world of the Wizard of Oz and it is perfectly fine, no one can sue you for using the Wizard of Oz name or ideas or characters.
Transformative Work/Fair Use Now I won't get into too much detail about these, but know this: You can not claim your work to be Transformative Work/Fair Use and think that will save you. These are not things you can add, these are actual legal terms with meaning. Fair Use is a legal defense strategy, where you try to prove that your usage of someone's IP or property does not detract from the monetary value of the IP. Transformative Works is a legal term too, which allows an artist to use IP so long as they transform it enough and build enough original content on it that it is considered a new and separate property. Such as, if you have a made a research paper and you end with a hypothesis, I can take your hypothesis and test it, write my own paper, and because the paper is 95% my work I can own the paper, and you have no claim to own my work. On youtube, you can copyright claim a video without needing to prove that it is causing monetary damage, and because of this, it is why youtube is known for having a terrible system because it doesn't protect its own creators.
A Licence is simple, you pay for permission to use something, you might be limited to what you can do with the IP but you can use it.For example, if you want to take a Daz3D model into a 3D video game, that is IP infraction on the 3D model, but you can buy a license for many of them separately, which allows you to use the model in a 3D video game. Paid Promotion means the IP owner pays YOU to use their product. Cigarette companies are famous for doing this in the early years of Television, where everyone would smoke. The idea is that if you are big enough, like Family guy, Having your stuff in their show acts as an advertisement. It is how lots of YouTubers make their money from things other than youtube ads.
Using made-up names is a quick and cheap work around this.
