You and I both know that they should be vented outside, but I’m guessing how often it isn’t would be quite frustrating.

My shitty starter house (1995) didn’t have a vent, but there was a window in the kitchen, so did that count? My boyfriend’s house is in a higher cost of living area with absurdly expensive houses, and he was told (after purchasing the house when he was getting some things updated) that his vented into the attic. He doesn’t use it because he doesn’t want to blow aerosolized oils all over whatever’s up there.