Because TBH when that last 10% of the game is going to take as much time as the first 90%, you can release the game at 90%, make up some money, and hopefully finish the game if its good, or at least recoup some of your investment.

There are more good quality especially indy games coming out right now than probably ever before, but the envelope pushing games and especially those with new an interesting gameplay is lowering. Genres are starting to really find their limits, and a huge amount of games are just hyper specializations of one mechanic or another, and the rest are playgrounds for many many different mechanics (but most/all of them already invented). Games then need to lean on maximizing story, art style, or precision mechanics and production quality to set themselves apart. Online delivery has made "light" publishers possible which is only a good thing IMO. Games like undertale, minecraft, stardew valley, rez, etc would have been extremely difficult to get going initially without online delivery.

VR can open up some new pathways for sure, but we'll see how that goes.