It isn't, necessarily, that camera technology improved. In fact, it wasn't until the early 1940s that innovations in tripod engineering allowed for anything smaller than a building to hold a camera.
In the 1930s camera makers figured "If we're going to have to hoist the thing on a building we may as well make it stunning!"
Miss Noribs on the left and Mr. Nofeet on the right would go home disappointed, again, all because the tripod was still in R&D.
Imagine the cargo pants pocket you'd need for one of those things.