Tumblr is designed for daydreamers

Constant daydreamers feel at home here. That dictates the demographics a bit: users that are young enough to have time for constant daydreaming, or the castoffs, eccentrics, artists, thinkers, weirdos, self obsessed, over sensitive, lonely, hungry, diluted, under employed, self conscious, and strange, who have found some way to carve a high functioning inner life from the demands of a more ‘linear’ world.

Nothing to add, nic-rad says it all.