I’d have thought the overwhelming majority of valves were developed for audio use; radio, communications, sound recording etc, both military and civilian. What are the other uses? Before computing came along I can only really think of lab test gear, oscilloscopes, signal generators etc, which mainly existed for developing the former! Radios, televisions, PAs, mixers, transmitters, guitar amps etc would have been the bulk of it, surely?
Here’s a fascinating RCA valve TV promo from 1956:
The
Computer History Archive Project is a really good Youtube channel with loads of amazing footage of early technology in action.