If I think I have an edge making a bet, I will bet this line. It doesn't really matter to me, if I end up with 1, 2 or 15 wagers for a certain day as long as I think, the book made a mistake with that certain number or spread for a game.
I love betting player props, especially on pitchers in baseball, and due to the limits I can't put more than 200-250$ on a single prop bet most of the time. But depending on the schedule and the lines there are mostly between 2-10 prop bets alone any given night, I really like because of the imo soft lines and most of the time there are 1-4 money- or runlines, totals or 1st 5 inning wagers in addition to that.
Besides that I follow some guys and have regularly action on some soccer games from different European leagues.
Of corse, like bas said, I could put my stake on the game with the biggest edge in my opinion, but I like to spread my action a little bit and don't want to have too much money riding on a single game/bet, but on the other hand I also want to get as much of my bankroll as possible into play every night in +EV bets.
Another advantage would be limits: If I wanted to put my total stake for a given night on one single game, I could get into trouble because of limits (f.e. propbets for MLB or some exotic soccer league like 4th division Norway or 3rd division Poland)...