I think it helps to have played a sport before to appreciate watching it.
For example, when I was younger I used to play some football (soccer). I don't play at the moment, but when I watch a game there's a lot more for me to pick up on because of that past experience. I get that to someone who's never played before the game might look uninteresting as it's a relatively low point scoring game (compared to something like basketball or tennis), but to people who are into it there's much more going on than just the goals, it's the dynamics of the game as a whole that captures their attention. Having past experience playing makes it easier to see when a team is attacking well and defending well, easier to pick up on individual displays of skill, easier to pick up on new opportunities and how these could change the game, easier to pick up on the state of the game (chances of a win, loss or draw) and the ways the players respond to this.
If the only part of the game that mattered was when the ball was kicked in the net then it would be a boring game as it doesn't happen very often, but there's a whole lot more going on if you know where to look. You might still find the game boring, but hopefully this helps to explain how people get into it.
I don't doubt that that really deepens your appreciation, but I think even through repeated watching you can come to appreciate the game more. To give the most obvious example, someone without a lot of familiarity with football would probably be confused about why they were go back five yards behind where they were after the last play instead of the last place they got to because the penalty system isn't obvious to a neophyte (in soccer terms, consider how many people are baffled by off-side calls if they only ever watch a few games during the World Cup every four years).
I'm not even sure if your references to football and soccer are the same sport, or two different sports. I think they usually mean the same thing, except in certain countries where other sports (such as rugby) are called football instead.
I'm from the UK, we call soccer "football" here. The sport that people in the US call "football" we call "American Football". Many countries call soccer "football" (or variations thereof, depending on their native language). I've never heard anyone use the term "football" to describe rugby, though rugby (union) was supposedly a spinoff from football (rugby league came later). To add to the confusion, there are two other sports that have the name football, namely Gaelic Football and Aussie Rules Football, both of which are popular in their home countries.
I originated in New Zealand, and football generally meant rugby. Maybe things have changed since then or maybe I don't remember correctly.
I didn't realise American football could be abbreviated to football. We also knew it as gridiron, and it always seemed like the very definition of boring, repetitive sport. Guy takes the ball, runs at the opposition, is taken down, everybody stands around chatting for ~10 minutes, repeat :)
