It's simple, buddy, creating such games requires time, computing power and a lot of creative work. When a person makes an effort, it is quite natural that he has a desire to receive financial compensation for the efforts made.
Another thing, and this is the main thing, is that there are those who are ready to support the developer financially, thanks to these people, others have the opportunity to receive content absolutely for free, you just need to wait a little.
Not only that but, in order to get the resources just to do Simple stuff costs a lot of money. For example, a basic Daz3D set is free but you have to pay for stuff like a Genesis 8 female model
15-16 USD, the same for a male. Certain scenery for backgrounds costs between 12-16 USD each. Male and female head shapes, 15 USD each. Gowns and dresses for adult females between 18 and 28 USD each. A certain lingerie set @ 12-18 USD, and so on. Just adding up what I just mentioned can total over 100 USD.
As you try to be more specific, each additional set for things like body morphing, hair, lips, eyes, skin textures, etc. begins to add up. If you're a first time dev, the prices begin to get daunting. Sure, Daz and others have free supplemental programs out there but you still need, and have to pay for, the base kits to make the renders look worthwhile. As you add more models like young adults, children, old adults, pets, plants and others, you need Some kind of comp to offset the losses. The thing is, if you have a job to go to, those expenditures can take away from your living expenses. If you don't have a full-time job, privatizing is a Must.
Several years back, I got the Daz starter program. Before I did anything else, I decided to go to the Daz Store, pricing all of the assets. I gave up that notion quickly because it was going to be a finance drain. THAT's why I'm supportive of those devs who have, not only the moxie to start but to continue their work. Yeah, you can save a lot of stuff BUT you gotta Get them first. Which is why, even though some people think that my comments of support are cheesy, I try to be encouraging. It costs time, money and mental fortitude to do what the good devs do and why I find it ridiculously stupid to gripe about something that Many here have No inclination to support financially, even if a dev says "Buy me a coffee". So kudus to those folks out there that stick it out despite some of the venomous and ridiculous criticism that's thrown their way. As the old saying goes, "You don't know a person's journey until you walk a mile in their shoes."