I believe it depends on the people and their dynamic.

Fetishists typically know what they want, even if some lie about it out of embarrassment or because they are trying to impress the Domme. Submissives can get more confused about what they want, in my experience. Some also go in cycles where they are really into serving and submitting, and then they want to completely distance themselves from anything BDSM.

When a sub leaves, we Dommes don't necessarily know why, unless the sub honestly tells us. I might not like to hear that they're now serving someone who's got a multi-room dungeon, or who is closer to their office, or who expects minimal tribute, but we all have our preferences. I have found that most steady subs who disappear, at least try to return later.