In other words, you now have some amount of "blind spot" for motorcycles--but only motorcycles. Whereas, with the mirrors adjusted further in, you still have some blind spot for motorcycles--though perhaps less than with them adjusted further out--but you also now have a blind spot for cars, which you don't have with the mirrors adjusted further out. And cars are much more common than motorcycles, so adjusting the mirrors further out is a net gain in how many vehicles you can see with the mirrors.

An even better solution is cameras like the ones that some higher end vehicles now have for changing lanes. In the ones I've seen, when you turn on your turn signal, your vehicle's screen (the one that shows the backup camera image when you're in reverse) shows a view of everything on that side of your vehicle. No blind spot for anything. Eventually I'm hoping this will become mainstream (the way backup cameras are getting to be).