To make one's bed in a tree is easier - and quicker! - than to build oneself a house for the night, [he says lightly. Which is to say something like "I don't mind houses per se (especially if the house in question isn't provided by a kidnapping magical world), but I'm completely comfortable sleeping in trees, too".]
But Men, I have learned, seldom share Elves' thoughts on ease and comfort. You are used to having a proper bed always?