You need to compare the odds of winning to the payout to figure out what is a good bet.
On dice sites, there is nothing to figure out. It is set in stone. For sports betting, the odds of winning are not set in stone. The oddsmaker sets the individual odds for each game, they can make a mistake or the situation can change (player gets hurt,importance of the game changes, etc) so you can make a "smart" bet that has a positive expected value for you. A smart bet doesn't mean you are going to win, but it's possible in sports betting, it's not on dice site.
Pretty much.
In dice, you have noone to outplay or outsmart. In sport betting you have 2 entities you are "playing against" - the traders, who set the initial odds, and the crowd, who moves the line by betting on either side. If you have an informational edge over either of them - you can make money in the long run.
Its not an easy task though, you have to put a lot of time and effort into it.