they were never popular even during the days of robot wars as they were never given much coverage. All the bots shown on tv were always heavyweights unless you looked to robot wars extreme. battlebots by contrast showed many different weight classes and so that's the reason there are more diverse numbers of bots in the US.

I don't think it's a bad thing. You want to play big, head for the heavyweights, you want to have smaller bots that can be handled by a single person, you go for the featherweights. Dilluting an already small group of people into middle ground weight classes wouldn't do much good imo.

I believe it could under current rules (would need to check) but you'd need at least two machines to compete and robochallenge to host it.