Thousands did / do. The vast majority of League players in England are strictly amateur and always have been. They mostly play on municipal park pitches; the Union teams tend to have far superior facilities. I played Union at school and League later.
The main reason League came into being in England was based on the British class system. Professionalism was what the Establishment used as an excuse to keep the great unwashed from dominating their sport.
I am talking from the Australian perspective. Amateurism in sport is a whole subject on its own merits. Hard for people to get their minds around the fact that the vast majority of international sports used to be either amateur, or divided into amateur and professional vectors.
Loig in Australia has been aggressively professional for as long as I can remember, whereas rugby is still, at heart, a sport for people who love it.
Loig enjoyed its huge expansionary phase primarily because of the advent of licences clubs in N.S.W.
My best friend, a very good rugby player and State level athlete, became a schoolteacher and got married young. He needed money, and so instead of staying in rugby (where he could have risen to the top) he starting playing what used to be called park footy for Guildford in Sydney's west. He was one of a handful of professionals on the team, after the match he and the other paid players lined up and were handed ten quid notes straight out of the bar takings by the manager of the licences club. In those days a young teacher earned about twenty quid a week, so this made all the difference to him and his young family.
He did not enjoy playing, he said it was pretty unpleasant because of the total lack of camaraderie and enjoyment amongst the playing group, who spent all their time, on and off the field, manoeuvring to earn more money.
It is interesting to speculate how loig might have developed had they had not had the poker machine money, which was huge and unregulated for many years.