Fair enough, but I guess it becomes a bit meaningless in my eyes to label something a stealth tax if that just means not a tax but rather anything that the poor and stupid choose to spend money on (I appreciate your position is probably more nuanced that this). I just look at gambling and think, is it really that stealthy? I mean with all the regulation now it gets labelled as gambling, warning notices all over the place, age restricted, max wager limits, bans on advertising during certain hours / mid-match, minimum proportion of advertising that has to be spent on responsible gambling guidance etc - it's about as un-stealthy as I can imagine.
Something like car insurance, I could maybe see an argument for being a stealth tax, because people that choose to drive a car (deemed important by a lot of people) have no option but to buy it. Gambling though doesn't come hand-in-hand as a mandatory bolt-on to other activities, so it's neither particularly stealthy nor taxy IMO.