Partly because I am a huge fan and partly because it is a regular source of income for me.
I suppose it started as a sport you liked and then you realised you could make some money out of it? Is NFL the best sport to make +EV bets on or could you do the same on English football or similar? i met a pro sports better once who made most of his money betting on Aussie football, he studied the game and reckoned he knew it better than the bookmakers. I heard of another guy today who left work to bet on sports and he's having to sell his £500K house to pay off his losses.
ATM poker has to be the easiest way to earn a living gambling right? Probably won't be for ever of course.
Leaving your last question aside as outside the scope of this thread!
I loved the sport, played it a bit and got obsessive about it. Soon I thought I knew as much about it as the experts, and certainly stood a chance relative to UK odds-makers. This was back in the old days, these days the odds tend to be priced off the Vegas sportsbooks
However a proliferation of betting mechanisms (betfair, spread betting firms, novelty bets) now mean that it is possible to find value on any given sunday.
I make a five figure sum each season...but do not except for very small stakes and a bit of fun do any betting on English sports.
eg Yesterday the 5-2 Denver Broncos are away at the 2-5 Pittsburgh Steelers. Pittsburgh are priced odds on because they are reigning superbowl champions and because they are at home. Yet Denver have the best defense in the league and ran the Colts close the week before.
The bookies simply got it wrong pricing the Bronocos at odds against (5/4..6/4 in places)
The Broncos led comfortably all game and were never threatened.
I now write a weekly NFL Column for a sports betting site and so far this year I am a 60% tipster on there. Anything approaching 65% across all the games is very good, as the potential for upsets in the league is high due to team parity