There are at least 5 different ways to configure a sleeping space in a tiny house:
I don't really like climbing down ladders. The biggest argument I could come up with against having a loft was that you typically need to climb a ladder to access it. Going up might be OK, but coming back down would be more of a problem. I didn't really fancy having to negotiate a ladder half-asleep in the dark at 3am if I need to go downstairs to pee. But I've seen some very clever stair designs in tiny houses, which double as storage spaces, so that immediately felt like the right solution for me.
Skylights are very common in tiny house lofts, and it's not hard to see why. For a tiny house with a traditional gable roof, there isn't really anywhere else in the loft to put windows. Just having a single window in the gable end probably doesn't let in quite enough light.