I don't understand ASIO. I don't understand VST. I get that they both make my life easier. I totally get that. I mean, until they crash at least.
One day I'm going to go to a whole lot of trouble to really "get" at least one of these things. I have to figure out hardware monitoring. Right now I seem to be both hardware and software monitoring because I get this delay on anything I record (in the monitors, not in the actual recording.)
Anyway, ASIO. It lowers the latency of recordings. It makes it easier to use software instruments.
I suspect that the relative lack of ease for ASIO making instant sense to everyone is that every software/hardware combination is completely different.
I'm using Samplitude (Sound on Sound review here) with a MOTU UltraLite interface (with an Apogee Mini-Me as the master clock and the analog inputs for the S/Pdif input on the UltraLite -- let me tell you, the Apogee clock on the UltraLite makes a very audible difference).
But one day. Oh yes one day. I will understand them.