I can't understand the logic of "it's just a hobby" and "why all these unfinished and abandoned games" coexisting in someone's head. If it is someone's hobby they can do whatever the fuck they want and dropping the project is what a lot choose to do. Along with all the other unfinished projects people have like fixing up a table or restoring a car. Yet people will still complain even when a dev
doesn't take any money and abandons their project.
As a hobby, adult game development is not exactly fun, it ain't cheap, and toxic public spaces will wear you down. Let's go through a scenario where you are dev making "yet another Daz visual novel" and hoping for it to be somewhat "successful" (popular and/or monetary support wise).
Fundamentally, art is by far the biggest factor in the development time spent making an adult game. Programs like Daz allow people who can't draw (like me) the ability to make something that would otherwise be impossible for them. The difference between sfw games and adult games is almost everything is "handmade". Meaning most adult games don't get the luxury of making a pickaxe swinging animation and hit sound that will be used over and over again. Every scene has to be different and creating all the needed art is a far more staggering obstacle than most realize. And that is after using premade assets, skipping a huge portion of real-world game development like modeling, rigging, texturing, etc.
New devs don't know what they don't know, and one of the biggest reality checks is ambition colliding with skillset. There are so many things that you would think are relatively simple that turn out to be monumental nightmares to actually make. Take anything to do with water as an example, we all know what a wet human should look like. To get one single shot of a wet character in the shower you need the shower and the water drops to set the scene (steam, water drops on the walls, and puddles on the floor are usually skipped over entirely). Then you need a wet hair asset and a wet skin asset. And if you want to add sex to the mix, then all of that stuff has to be compatible with the genitalia you chose (hope you didn't choose the "wrong" one). If anything is off just a smidge, it can kill the suspension of disbelief. This is why most adult games don't have any (or good) animations either. It's hard enough to make static images, creating smooth believable motion is exponentially more difficult and time-consuming.
Despite how much an "entry-level" program like Daz touts itself to be, it is not plug and play. The amount of manual adjustment required to make renders look above average could drive you nuts. On top of learning a 3D rendering program, you also need to learn Ren'Py or some other engine to deliver the art. Devs also need to market themselves and make posts/content for Patreon or try to get their stuff trending on Twitter, Reddit, etc. Whether hobby or professional, anyone creating content wants it to be seen.
And it doesn't stop there, because once you start interacting with the audience it is overwhelming, to say the least. Everyone wants something different, and some don't so much request things as demand them (like "No animations for a game released in this day and age? C'mon, add animations."). Not to mention there are an endless array of chucklefucks throwing around their 2 cents in a currency that is only valuable to them. This leads to setting up a Discord server to filter some of the toxicity out and now you have to monitor that too. You may get helpful people that join or you might end up with a ghost town, it's a total crap shoot.
So now the time set aside for developing the game is stretched significantly between all these other things when all you wanted to do was make a bunch of lewd scenes with the fetishes you liked. The hours dedicated to the project per week either have to expand to accommodate or actual game development time has to shrink. Neither option is pleasant. You start seeing free time as "I need to work on my game" and feel guilty if you aren't steadily delivering content to your supporters.
This was supposed to be a fun hobby right? Where did it all go wrong?
In summation, the initial monetary cost is high (even excluding hardware), unless already heavily experienced you often need to buy more stuff you didn't account for, and the return on this investment is far below minimum wage unless you hit big (or make borderline illegal loli stuff). Then add on all the extraneous marketing that doesn't involve making lewd scenes and you have a recipe for the current state of adult games. Newer devs come in bright-eyed and bushy-tailed, only to be utterly stomped into the dirt by the reality that most of the monetarily successful devs have already been around for years, and these noob devs basically walked into a money pit. And if they want to continue doing this for "fun", they have to bankroll the ongoing costs themselves or give up.
In conclusion, there are very few people with the time, money, and wherewithal to get into adult game development and stick with it. Anything more serious than creating a short demo or dicking around for a thrill requires several orders of magnitude more time, money, and wherewithal to dedicate to a longer project. Adult game devs are not a lewd version of Tolkien, we don't just sit at PC for years creating sexy stuff before showing to it off for the world to see. It is completely unreasonable to suggest that a new developer starts out of the gate with a completed game that contains 10+ hours of content.