Question

Why is velocity and not just speed important to these pilots?

Answer 1

We're not sure which pilots you're talking about, but we can be sure
that whichever ones they are, velocity is more important to them than
just plain speed is.

Velocity is speed AND its direction.  I can clearly recall that when I was
taking flying lessons, and later flying solo with nobody else in the airplane
to get me out of a jam, it was not enough to know that my airspeed was
90 miles per hour.  I also needed to know at ALL times that my velocity
was NOT pointed straight at the ground. 

Happily, I knew, even back then, the difference between velocity and
just-plain-speed, and I'm sure that that is a big part of the reason that
I am here today to tell you the tale.