Gambling has been a big reason for the NFL's success in recent years. When you have money on a game you otherwise would not be interested in, the game suddenly becomes a whole lot more interesting. Well, that's my thought at least. It is one reason fantasy football has helped as well. When you've got players on random teams, suddenly you find yourself more interested in those games.
However.......if you are gambling on preseason games, I don't know what to say. It seems like if you are betting on preseason games to win money, you either know as much about the NFL as anybody, or you think gambling on preseason games is more entertaining than burning your money. I suggest the former because it is possible you follow the entire league and have a decent idea who has what kind of depth at the end of their roster. I suggest the latter because some people just like gambling for gambling's sake.
For our purposes, the 49ers are three points favorites tonight. They opened as four point favorites, but the line has come down a point. I suppose people think the 49ers starters will be sitting, but I actually think this is a winnable game for the 49ers. They appear to have a lot of depth, which would seem to benefit a preseason performance. When you're getting a lot of playing time for second, third and fourth string players, having solid depth is important if you're actually looking to win. Of course, if the 49ers are going entirely vanilla on offense and defense, as expected, maybe the depth won't matter.