Betting on sports is gambling and there is no other explanation about this. I don't think it is investment or anything else than gambling. Anything whatever is called where risk factor is involved is purely form of gambling. Putting on stake and having chances of loosing is gambling and in sports betting we sometimes loose and sometimes win so it is gambling and is same.
Exactly what you said. Investments, trading, sports betting, all of them are under gambling because of the risk factor involved in them, although only with a little variation of time it takes to get results.
I know some people don't consider sports betting gambling since you 'only' bet and you can win easy if you know the right information, but the fact is that it's not always true at all cases because there are always those unpredictable factors that can occur anytime.
I will never considered trading is gambling because gambling are giving fun for people not for making a profit unlike trading. we know they are the same risk but trading is good for making profit with low risk than gambling..