On one hand, this is actively bad for people. You can make the argument that some people win, but the vast majority do not (over any extended period of time). People are hurting themselves and the people around them. I personally know so many young guys who have lost thousands of dollars that they really didn't have the opportunity to lose on sports betting in the last few years.
On the other hand, why would I restrict someone's freedom to choose to make a poor decision?
I find this so hard to make a personal judgement on because I see myself going both ways in my own life. I drink alcohol despite it being bad for my health, but I scoff at smoking cigarettes for the same reason. You can actively justify either of these, but that's not the point I'm trying to make. I just don't know where we begin to restrict people's choices when it primarily affects them - the obvious exception being their friends and family who are affected as well.
Do we step in and prevent this transitive negative effect? I'm really not sure.
I've seen some other comments mention having heavier regulation. That idea makes sense as a middle ground to me, I guess (although I'm really not sure).
Ok, let's ignore the individual. But gambling losses that lead to bankruptcy hurt creditor, for instance. Since creditors can't really easily separate out gamblers from non-gamblers, those defaults get spread across society as costs.
The linked article asserts that a large proportion of government welfare funds in Brazil are gambled away.
The linked article asserts that losses inspire domestic abuse. Consider that net winners may only win 51% of the time-- that's a lot of losses even if the individual makes out better in the long run.