Beyond the fun of enjoying a good story, I also prefer consistency in regards to how the rules are used by the DM or players. You can tell by the DM's style if they like to make stuff up on the fly, or like tinkering with the rules. My biggest concern is consistency. If the DM changes things too much and too often, then it is harder as a player to adapt or trust the DM.
There are a lot of players that develop characters based on certain expectations on how the rules will play out or how they are interpreted. If that starts to fall apart or is less reliable based on how the DM uses the rules then I can understand the apprehension. I have played with DMs that had very detailed worlds, rich plots, and interesting characters, but they also had no problem changing rules interpretations on a dime to suite their needs. I never lasted long in those campaigns, and even if I approached the DM, it was rare they would change.
There are a lot of players that develop characters based on certain expectations on how the rules will play out or how they are interpreted. If that starts to fall apart or is less reliable based on how the DM uses the rules then I can understand the apprehension. I have played with DMs that had very detailed worlds, rich plots, and interesting characters, but they also had no problem changing rules interpretations on a dime to suite their needs. I never lasted long in those campaigns, and even if I approached the DM, it was rare they would change.