They also throw away their skill. Yeah, sure, exposure; you know what exposure does? It kills people. If you take the more capable and cooperative specimens and pair them up with people who know their way around something like Unity or UE and someone who isn't completely useless at business, you quickly end up with quite a capable little studio that can do fun projects (of limited scope, but there's something to say for games that have actual focus) without being beholden to someone like Bethesda churning out just barely playable titles in the hopes that Modders Will Fix It.
Mods these days seem to be (with only moderate exaggeration) either "N00d Mod OMG"/"OP weapon 9001", or "look at this amazing full conversion that took five years to make and will be shut down by a horde of attack lawyers because I'm using Blizzard assets on on a cracked Nintendo!" with surprisingly little middle ground.
Not really sure what games you've been playing but there are dozens of games out there where the best content by far is made by the community. The ARMA series has literally thousands of mods which vary in quality but the best of them are way better than anything that ships with the game itself. Cities skylines has a great modding community, as does the flight sim series to name but three, there are many more so I respectfully disagree with your post.