The answer is already there and given by many and there's the distinction between a sport and gambling. Football is a sport and in gambling, there can be any other activity that can be applied to it.
Plus, it also depends on the country that prohibits gambling. If they're a Muslim country then we can easily understand that it's about the belief and that's the same with other countries that prohibits it.
Correct, you can gamble on whatever including politics, economics, etc. The distance between football and gambling is equal to the distance between the Earth and Mars.
That just sets the boundary and difference of it.
It's entirely different and we're just used to the type of gambling with sports and we always see bookmakers and that's probably why when it comes to sports, the first thing that comes to our minds is all about gambling.
Because for a long time, it's always associated with it but not just because there's a sport, it's always connected to it, it's not like that.