Yeah, there's certainly a problem with bleed for a lot of characters and players. I've also had issues with people who get too attached to a particular concept and storyline; they want to be the prince who goes out and slays the dragon, for instance, but they never communicated this to the GM so they wind up upset when the story takes a different path.

One of the problems that comes into this (and I wish I remembered better who was the first person who I found to describe it really well, so I could give them credit) is that a lot of people get trained in adversarial or self-focused roleplaying by their experiences with other media.

For instance, a player doesn't say what they want their character to be able to do because their goal is to bring the world to its knees until they get what they want. Perfect in a sandbox, but not great if the GM is spending all this time preparing courtly drama and their plans get sunk by one player wanting to go and explore the lost ruins of Lemuria.

Alternatively, players get in a rut where they think that they're the only person who can move the story forward or describe their character at all, and have problems accepting the mechanics and conventions needed to keep things from going off the rails.

There's a reason I plan to devote a whole article to characters, and it's because I've seen a lot of great, and a lot of really troublesome, characters over the years.