Pancake servo motors?

Hi all I have been exploring various refits and following along with
various threads bu I
don't see anyone mention the ironless type pancake motors.

For electric controls we have been using the ironless pancake style
motors exclusively
for years now. These motors such as the Kollmorgen servodisc or
Infranor motors would
seem also ideal for high performance servo systems on machine tooling.

The rotor design provides almost zero cogging , very long brush life
in brushed models due to the low inductance, very high acceleration
rates and peak torque. It also seems the flat package would just look
nice compared to a big long servo motor sticking out in some
applications.

Does anyone have experience as to why these type motors are not
appropriate I really don't see a down side other than the diameter
and non NEMA mount which would seem easy enough to get around?

Anyhow just a question as there are a lot of experienced folks out
here.

Brian S Punkar
BSP