"Basement" is not usually bad in these cases. The image that comes to mind is a finished basement with a separate (or at least semi-private entrance).

I think "basement" has become synonymous with these cases because: 1. It reflects that the person is at least semi-independent (as opposed to children who live within the same space as the parents) 2. It is a bit insulting, reflecting society's view of the situation (it subtly implies antisocial behavior... The basement gamer, for example)

Basements are usually a fairly large single room, usually well away from the commonly traversed areas of the house. These things appeal to grown males living with their parents because they can be louder, have more space, be more private, etc.

Not only that, but in some suburban houses, they even turn the basement into a separate apartment and rent it out after the kids have left the house.

While the expression is living in your parent's basement, I don't think the kids are literally living in the basement unless the parents happen to have a home with a nice finished basement which is nicer to live in than an upstairs bedroom. It's just an expression.

I second this. Unless the person has lived their entire life in the basement (which seems a little cruel) why has the person been moved to the basement after reaching adulthood? Why can't they keep their room?

Basements in the US are really nice. As other have said, they are typically really big (usually the entire foot print of the house above), isolated and sometimes have their own entrances.

My parents moved my sister into the basement when she grew up because it was basically an apartment. It was a lot bigger than her bedroom, and offered her the chance to accumulate some furniture and stuff that she would need when she moved out.

>Why can't they keep their room?

The basement is an upgrade. It's virtually a bachelor apartment (or a flat, for the Europeans reading), often with its own access, a private bathroom and often a kitchen or kitchenette. They're actually lux enough that they do very well on the rental market in busy cities.

For the child of the adult owners, it's a sort of independent-dependence. Some move down there while trying to save money for their own dwelling, which is probably the most often case, and others move down there, never strive for independence and become the stereotype talked about in this thread.

Maybe the parents want to have loud sex without their mid-30's child hearing them from his bedroom down the hall.

I think it comes from the trend where the storage basement got converted to a room for the older kid.

Providing a big room and privacy for parents and kids.

I'm not sure how it is in other countries, but if you look at the rental market in the US, it is fairly common to see the basement rented out as an entirely seperate unit.