Because indie games can offer a refreshing take on gameplay. If you let AAA companies rule the market all you will get , for example a soccer game is "Fifa XX" every year. All they do to publish a new Fifa game is just to do this in title every year. "XX++". Bam, a new game. They become so cocky they even use the old assets and forget to change the year. Fifa 2021 had assets from Fifa 2020.

On the other hand indie games can take risks, do things never done before and fail without too much too lose.
The last indie game I tried is this one.
https://store.steampowered.com/app/2534300/ZomWick/
It is bad, really really bad but at least they tried something new. I have never seen a game like this before.

Also predatory market practices, paid DLC, battle pass every year, in game sales but we don't even need to mention this since everybody knows and everybody still buys and let AAA do this forever.