Voice unrecognition

So what’s the deal with automated phone systems that make you respond via speech rather than by pushing buttons? Most of the credit card companies I’ve called in the last six months have a system like this, and at least one of them offers you no option to press a button at all.

I could downgrade this gripe from vexing to just plain annoying if only I understood what purpose it served. How does it benefit either party to have customers use an unreliable (at best) voice recognition system? How is that advantageous over pushing buttons?

The mind boggles.