Fifteen blinds in the small blind is 89 hands, 46% of combos: any ace, any pair, suited kings in full and offsuit kings from K6o, queens from Q4s and Q8o, jacks from J5s and J8o, tens from T6s and T8o, 76s and 86s.
Push from SB, 15 BB stack
The SB is the only position where the shove at 15 BB remains the main line for almost half the deck. The reason is the structure of the spot: raise-folding against the big blind works poorly — he has the closing position and perfect odds for a re-shove, to which you'll fold everything you raised for. The all-in cancels that option: now he is the one making the decision with the risk attached.
It helps to see how the fifteen differs from 10 BB: K2o–K5o, Q6o–Q7o, J7o, T7o, 65s are gone — the bottom that lived off the stack being cheap. But look at what stayed: T8o, Q8o, 76s. The range is still wider than the button's at 5 BB.
Alternative strategies — limping or a small raise with balanced ranges — become justified deeper than 15–20 BB or with antes; without them, the shove is simpler, harder to get wrong and almost as profitable. Compare with 20 BB, where the choice is no longer clear-cut.