New candles take longer to light the first time. If you’re using fresh birthday candles take a moment and light them before your party starts. It’ll burn off the excess fuzz/residue/wax on the wick. Only takes a few seconds to do this. Then extinguish and stick ’em in your cake.
Having been ‘primed’ the candles will light more quickly the second time around. No excess fuzz/residue/wax will drop onto your cake either. When the pressure is on with excited birthday party kids at your kitchen table pounding their forks you’ll appreciate those seconds you saved.