Why don't voice radio communications use FM?

Vaughn Simon writes:

Such as VOIP actually, or other digital technologies that are now quite
common, cheap, and "off the shelf". In police and fire communications, FM is
quickly giving away to digital modes.

I doubt that they are using VoIP, though, which is notoriously
unreliable.

I'm not sure that cheap, common or "off-the-shelf" should be the top
criteria for choosing a replacement for AM radio. I think "safe"
should be the highest priority. If it improves safety, it's good; if
it doesn't, it's bad (unless it can improve something else _without_
compromising safety).

A digital-capable radio does not care if it is transmitting voice or data, so it
could someday allow truly automated flight control. For example, you might be
able to get clearance into controlled airspace automatically and have it show up
as a green dotted line on your MFD, to be acknowledged with the mere push of a
button.

But then you won't need pilots. Actually, it is nearly possible to do
without them today--but radio communication is still one of the
sticking points.

--
Transpose mxsmanic and gmail to reach me by e-mail.