The wider and flat crate makes for a nice stepping stone for trying to get to higher ground. Think of the wider dynamite labeled mining crate, but MUCH wide and easier to hop up onto, with more space as well, giving Engineers the potential to put buildings atop of it, unlike the smaller mining crate.
The wider and tall crate makes for good cover without that annoying gap that you would get if you were to place two taller barrel crates beside one another, instead of just this one, for example. Overall, some people may think they look "cursed", but I feel like there is a lot of utility in gameplay-centric props like this. Very useful! Thanks again, FGD5!