Because they can still be great games. Rust was in early access for years but it was always playable and fun. 7 days to die is on alpha build 21 and has been in alpha for I don't know how long but it's amazing. Valheim was basically perfect from the start even if it was missing the whole end half of the game.

Palworld is a very good start. There's a bunch of QOL changes and bug fixes that would improve it, but the core gameplay loop is established and the parameters are all selectable so you can tailor the difficulty as you please. Evidently the "goal" of the game is blocked off, but aside from that it's a full game. No man's sky and starfield were honestly less finished on release.

If the devs are good, those early access players make the game better for the people who buy when it's fully released.