The reality is probably closer to the flightily nature of us as gamers - We mostly just want to try the game because some part of it seems fun, if that can be tried for free with a demo, why buy it now that we got our fix? Why would a big AAA take that risk?

The study was they tracked sales across multiple games for years, here’s the first example I came across in the wild from ten years ago: https://www.youtube.com/watch?v=us6OPbYtKBM&t=640s

Developer here - currently indie but was in the machine at one point. Cold hard fact is that demos hurt sales for AAA games, and pre-orders get cash in the door today to keep the lights on. With millions and years invested, they must hedge and limit risk as hard and as quickly as possible.