I agree with your posts @GasPanic.
I'm not a gambler. I don't even buy a lottery ticket (mainly because I'm never organised enough!). I have occasionally bought a lottery ticket in the past and when my dad was alive, we used to place an annual bet on the Grand National.
I'm cautious by nature. Risk doesn't appeal to me.
However, all of that being said, it's not my decision to judge whether spending £5, £10 or £100 on gambling is a "waste of time".
Gambling is enjoyable to some people. Some people enjoy the thrill of spinning slots, or watching the horse race and cheering for their one to romp home. You might not win, but gambling is an experience just like any other activity.
You might not like the idea - but no one is asking for your approval. And therein lies the point. Gambling is legal. There are different types of gambling. Some people get addicted to it. Some people don't. The same could be said of alcohol or cigarettes.
Lots of people who gamble enjoy the "experience" of gambling and even if they don't win, they've been entertained for the period of time they've been betting/playing. Look at casinos - lots of people visit them and never win a thing but the whole casino experience is fun (if you enjoy that kind of thing).
Gambling is no different to smoking a cigarette, or having a pint at the pub. Nothing to show for it other than a personal experience that was enjoyable. It may or may not be a good idea, but it's legal and it's no one else's business.
Of course, as an individual, you have the right to decide if your partner is indulging in things that you're not comfortable with. We see it on MN all the time - porn, smoking, drugs, drinking etc. You set your own boundaries - but that's very different to believing you have the "right" to tell someone that their hobby is "a waste of time".
The trouble is that there's a narrative that all gambling leads to addiction and is a terrible thing. That's like saying all alcohol leads to alcoholism and is a terrible thing. Both can lead to problems - but won't for everyone. Imagine if your partner "told you off" for having a glass of wine because of the risks of alcoholism....scolding someone for occasional, controlled gambling is the same principle.
Of course though, if you think your partner has a problem with gambling, then you should talk to them. In the same way that you should talk to them if they had a problem with alcohol. Or if you spot signs of a potential addiction spiralling. You should talk to them if they're spending family money, or they're spending more money than you've agreed. That's not because gambling in inherently "wrong" but because it's become a problem.
I would say that if someone HAS to gamble every day, there's a very big problem. That's addiction. Again, not everyone will become addicted but it's easy to fall down a slippery slope - the same as with other addictive substances whether that's painkillers, alcohol etc.
Aside from the moral arguments of gambling - OP, has your partner ever actually withdrawn the cash? Lots of freebie offers from online bookies have terms attached which mean you have to re-bet the money again a certain number of times before you can cash out. (I had to research gambling for my line of work, and tbh, the free spins/special offers just look like a big con).