It's a unique sport that is multi-dimensional. Athletics, skill, and strategy.

I mean, you have to be quick, but you better have power because that linebacker weighs as much as some cars. Got a lot of skill because you need to move the ball with a strict set of rules. Above all it's the strategy of the plays. I think it's because most people don't understand it because of the rules. Half the people watching it don't understand the rules. I admit there is a lot I don't know. I used to hate it because I thought it was boring until I understood the strategy part of it being as important, if not more important than the actual athletes themselves.

Cleats, shoulder pads helmet are kind of expensive. Also third world countries that struggle to feed themselves would be incapable of producing offensive linemen

1. it's not a cheap sport to have an organized league for... you need helmets, pads, cleats, goal posts, etc
2. there are some basic things that are pretty unintuitive and have a lot of jargon... the 4 downs, scoring system, formations, receiver eligibility, etc
3. it has a reputation for causing brain damage

Why play football when you can play soccer and rugby