I disagree - I think it would be a great idea. While some may argue that gambling is a zero-sum game (which isn't exactly great, in and of itself), it's really a net loss. While some people may win a bit of money, I'd argue that the degree to which their lives are improved is much less than the degree that some others' lives are destroyed. Gambling, ultimately, being a negative sum.
> Millions of people have started sports betting. If it becomes illegal, it won't make them stop
I disagree with this too. It's substantially easier for any random person to simply tap a few buttons on their phone to place a bet than to find and arrange opportunities with others to bet on sports or visit a brick & mortar betting site. The level of effort of placing a phone bet is so small (and with 24/7 access), you'd have a very hard time arguing that making OSB illegal would only marginally impact the amount of sports gambling taking place.
Bottom line: gambling is an addictive activity for all people and some more so than others. Limiting access to it will have a positive impact on pretty much everyone who does't own or work at a gambling company.