I used to keep venomous and also am old enough to have lived when and where the "original" Neodesha-style slant-fronts were built from fiberglass with a baby blue gel coat. Anyone else remember them? Whatever that company was sold the design to Neodesha who wanted to mold them from ABS.
So I've been using this design since before Neodesha was making them. And yes, I do have some thoughts.
I think Randy makes a good point - the cages do allow an out and up motion for hooking venomous snakes with a bulky old-school hook. The very open look to the front and the slope does allow for a very quick look to determine when a snake is (or isn't).
The lip on top being where it is allows a cage to be picked up and moved to an easier to work location, which can be helpful with venomous. That lip is somewhat centered front-to-back so you can pick up the cage and carry it almost like a suitcase. Not the safest thing to do with the vent location but that is how a lot of us did it back then.
All that aside, I never did like how much effort it took to slide the doors open. Even if you radiused the acrylic or glass edge, waxed the track, or whatever, you usually had to hold the cage with one hand so it wouldn't slide while opening the door. You also could not operate the door with a hook very easily. None of these things are safe with venomous.
At any rate, I think they caught on with the venomous crowd because they were secure, locking and unbreakable, especially the old fiberglass onces. Of course Coral Snakes can squeeze out of one but that rumor never really spread in the pre-internet days.
They were basically our only choice and I think that faction of keepers just started to associate them with "the right way" to keep those types of snakes.