They assume that any overcard drastically decreases their hand’s equity.

The reason many amateur players check-raise in this spot is because they don’t want to get outdrawn by various overcards. The correct play by far is to check-call because having 62% equity in a small pot is vastly superior to having 18% equity in a large pot. In order to profitably check-raise in this spot for value, you have to expect your opponent to raise preflop with an incredibly wide range and be willing to stack off with hands like A-J and 5-4 on the 9-4-3 flop, which is almost never the case. If you elect to check-call instead, you will have 62% equity against your opponent’s range (this assumes your opponent will continuation bet 100% of the time on this uncoordinated flop, which may or may not be the case). Assuming your straightforward opponent will only call your check-raise with top pair and better made hands, you will have about 17% equity when called. This is a horrible spot to check-raise because when your check-raise gets called, you will usually be against a range that contains almost entirely better made hands. You check and your opponent bets 4 big blinds into the 6.5 big blind pot. For example, a tight, straightforward player raises to 3 big blinds out of his 50 big blind effective stack from middle position and you call in the big blind with 9c-8c. Instead of check-raising for these reasons, many amateur players check-raise because they want to protect what they assume is the best hand at the moment.

In general, you want to check-raise the flop when you can extract value from many inferior made hands, when you can make many superior hands fold, or when your marginal value hand plays poorly on future betting rounds, usually because your opponent is overly aggressive and the board will significantly change. Recently I have been reviewing hands from small stakes poker tournaments for some of my private students and it seems like their opponents (amateur small stakes players) check-raise in exactly the wrong spots.

Poker raise call check