Were never folding here, so saying you would at least call is pretty meaningless (not trying to hate on you, just attempting to further the analysis). For simplicity, lets so i had 4k, and he had 3k to start the hand. After the flop, the pot is 750, I bet 300, he clicks it back (now the pot is 1650). If I call, he has 2100 with a pot of 1950. Thus, if I check the turn (remember all those scary cards we talked about) were giving him maximum fold equity on a turn shove. My all-in is to extract maximum value from TP with a good kicker, which I perceive to be the top of his range (aka hands he isn't going to fold). Shoving also prevents me from ever getting bluffed off the best hand, a reasonable scenario if we call or raise less than all in, and an ace or J comes.