People apparently bought them in large numbers when they were widely available before WWII, mostly Iver Johnson and H&R, although S&W were still offering a model in 1940. They were all chambered in less powerful rounds, though they weren't all small or pocket revolvers. Apparently the latch is the critical point in a top-break revolver but it's also a critical point in swing-out cylinder models, too. Webley probably had the strongest but they were never really sold commercially in this country. A Webley variation is still manufactured in India in .32, probably on original Webley machinery.
I'm sure the biggest selling point for break-tops between the wars was the low prices.
The biggest reason probably no one would introduce a break-top or any new revolver design of a small size, not a reproduction, is the presumed current preference for automatics. Before WWII, some German pistols were being sold but the only small automatic still being made was Colt's pocket model, plus one from--H&R at only two-thirds the price of the Colt.
Shoot low, sheriff. They're riding Shetlands!
Underneath the starry flag, civilize 'em with a Krag,
and return us to our own beloved homes!
Buy War Bonds.