This is one of the primary reasons I've always gravitated to more simple/malleable roles. My go to's are usually something along the lines of mercenary, treasure hunter, vagrants with a severe case of wanderlust, bright-eyed young adventurers, or any combination of those-- in part because it's just so simple to ICly explain their presence just about anywhere. Granted, it wouldn't be any fun if everyone did that, so I love to see what concepts other people come up with. Some of the creativity you see can be pretty impressive.
While I'll occasionally do more centralized roles for alts-- like soldiers in training, courtesans, farmers, localized craftsmen, etc-- my "main" usually always has a pretty go-wherever-they-please-whenever theme so that I can rationalize a completely open door near anywhere. Honestly, I probably run into more trouble rationalizing a character's presence due to their personality more-so than their careers. (IE: What is Mr. Broody Grumpy-Gus doing at a costume party? Oh, because the player wanted to subject him to it to a demeaning outfit, gotcha.)
I try not to obsess too much about it, though. I'll come up with something no matter what if the character is pressed for an explanation ICly. That said, I try to  avoid pushing other characters to explain their presences IC as well. It might come up in idle conversation sure, but if it seems like they'd rather stay vague or aren't sure, I'll try to change the subject.Â
Nonetheless, I agree that it's good for people to make some effort to avoid too blatantly contradicting themselves. Like someone else said, if your character introduces themselves as a guard for a city, but they're currently grifting around a tavern half way across the continent, it's only natural for a character to ICly respond with "So... what the hell are you doing here then?"
While I'll occasionally do more centralized roles for alts-- like soldiers in training, courtesans, farmers, localized craftsmen, etc-- my "main" usually always has a pretty go-wherever-they-please-whenever theme so that I can rationalize a completely open door near anywhere. Honestly, I probably run into more trouble rationalizing a character's presence due to their personality more-so than their careers. (IE: What is Mr. Broody Grumpy-Gus doing at a costume party? Oh, because the player wanted to subject him to it to a demeaning outfit, gotcha.)
I try not to obsess too much about it, though. I'll come up with something no matter what if the character is pressed for an explanation ICly. That said, I try to  avoid pushing other characters to explain their presences IC as well. It might come up in idle conversation sure, but if it seems like they'd rather stay vague or aren't sure, I'll try to change the subject.Â
Nonetheless, I agree that it's good for people to make some effort to avoid too blatantly contradicting themselves. Like someone else said, if your character introduces themselves as a guard for a city, but they're currently grifting around a tavern half way across the continent, it's only natural for a character to ICly respond with "So... what the hell are you doing here then?"
Always looking for new connections!