well maybe you can call with hands like aq or aj however with hands like 99 or 88 you only have 2 correct options. you either fold or shove. why calling is a bad choice?. because you are commiting an important amount of your stack with a medium pair which might lose lots of value on a high flop like ak2. also unlike aq or aj, medium pairs ( 66 to 99) are much stronger preflop than post flop even tens and jacks which i consider strong pairs arent that strong in some flops, so when you have a short stack you need to take risks and you should try to avoid playing weak postflop hands on the flop. with a hand like kq, aq or aj you can make a call and see if you hit something on the flop otherwise you can just fold the hand or you can try to make a
bluff specially on a dry flop.
with only 15bb i think shoving is the right option here because even if you still have 11-12 bb left to play after calling the raise you are commiting at least 20% of you stack in this hand, and hands like aq or aj are very strong postflop so unless villain is a very tight player, or there are other players involved in the hand or if its a near the bubble decision then you should shove all in with these hands.