It's called a "Dutch light" greenhouse, meaning it has sloped sides. It's is a bit more stable, since it has some characteristics of a triangle. And it admits more light to the outer areas of the floor, with of course a little more difficulty with access. And I think it's "cuter."
But also, (and I think this is really why makers like them) for the same roof size, Dutch walls let the maker call it a larger greenhouse. They always refer to the footprint. Yours would have to be advertised as 8x8 or less if it had vertical sides straight down from the eaves. The difference in the cost of glass is very little, nothing if the roof is a bit lower.
I always worry about winds. I once had a hoop house lift off. We can get some high winds, so my current greenhouse, has a section of utility pole running down that unusable space along the base, and the horizontal members are strapped to it. (Used the tractor to shove them in.) I happened to have the poles anyway. If the wind wants it now, it's going to have to lift 24 feet of very heavy wooden utility pole.
