I used to place small bets on live underdogs because I sometimes see the angle where a team can recover and complete a comeback. Even though it's nice to hit a big multiplier from the underdogs, it can easily make you greedy and assume it's manageable after winning a few times.
I've seen people bet on crazier things, like bet builders stacked on top of another, and then somehow hitting them all in a single day.
Dont bookies correct odds during live events? If someone was an underdog before the sport event its understandable why odds are high. If during game/fight that underdog performs not worse than a favourite, bookies wont keep same odds. For example if odds on Canada in football were +30.00 for draw against Brazil, but during game, its still 0:0 and there are 10min left to play, odds on Canada wont be same +30.00. It will be around, maybe 3.00, but that is not something impossible in my understanding.