Could be in any context. I do it a little on UFC fights but that’s a relatively low amount and I can afford I to lose any time I do. It seems like it’s becoming a really wide spread problem though, at least in the US. At the same time I don’t see why it should be illegal. Granted I also don’t think any drug should be illegal.
If it’s casual between friends, you do you so long as it’s consentual between all involved parties.
If it’s at a real and/or digital casino using real money, I draw the line. Don’t really support them personally.
If it’s something like an old PC casino game I played growing up where there’s typically no real loss besides your time, I’m okay with it. Same applies to games like Balatro or Clover Pit.
Advertising it? Haell nah!
Those online betting sites like the US ones where people have been using insider trading and tampering with sensitive equipment to win bets? Ban the hell out of them!
Sports betting? If it’s consentual between a few friends/coworkers, you do you. Otherwise, I wouldn’t support it because you don’t know whether or not any sore loser will do their best to harass you or worse.
As for legality, I am not a prune about it. Especially since my fursona loves the whole concept of random dice and card luck and at least the card and dice games ( when confirmed not to be rigged ) are mainly pure luck.