how can you not raise?

if you just call and the dealer only calls, you've gained only one bet from the dealer.

if you raise, you stand to win at least one more bet from the guy to your right if the dealer folds because he's not going to fold to a single raise. or, you stand to win several more bets based on the dealer either calling/re-raising and the guy to your right also calling/re-raising.

call never. raise always in this spot.