Why does wasp spray seem to not stay active when sprayed on a surface?

I have used two different wasp sprays on these red wasps that have taken up residence in my eaves by my door. The spray knocks them down but if you do not spray them again (or step on them) when they are on the ground most of the time they fly off. Spraying them a second time will eventually kill them. I assume those who fly off eventually succumb but do not know for sure.
But, immediately after I have sprayed the opening to the nest in the eaves more will land directly on the sprayed surface and enter seemingly with no ill effects.
Does it actually keep on killing like ant and roach spray or does it only work with direct contact?