Why don't we see castles atop plateaus or mesas?

Plateaus and mesas tend to be in steppes and deserts. Here are some good examples, like… Mongolia: (from Hotel Room Search). Or Arizona: (from Arizona Experience). In either picture, every place is either extremely poorly defended (the flat parts) or virtually inaccessible (the tall parts). read more

Some people still do live in castles (see link). Most castles are preserved as historic landmarks instead of private residences. Castles are not comfortable places to live, nowadays, because they are hard to heat and the upkeep is expensive. read more