Concur ^. One of the reasons the military boxing teams were so good in the 40's was the Colleges and military were sending the boxers back and forth.
Looks like they were using them like these: http://www.sugarrays.co.uk/shop/images/D/cushion 1.jpg The first example of two handed pad work I've seen is this: https://s-media-cache-ak0.pinimg.com/originals/67/ae/9c/67ae9cef03f508e8c91409cdd353bcac.jpg It's definitely come a long way. Especially compared to the heavybag, speedbag, jump rope, etc. Stewart used them really well, perhaps revolutionized the use of them. Mayweather popularized it to the mainstream.
There used to be a kool vid on here of the soviets using them in what looked like some point in the 60's
Lots of the greatest fighters never did pad work, I'm fairly sure of that. It's become more popular in this age, probably where awareness surrounding the dangers of constant sparring at a high level have increased. It's also popular with the ordinary fitness enthusiast who knows nothing about boxing.
