I agree with Campy.
There has to be a way in which you can add some bass or light ply so that you can screw the servo down.
They need the rubber vibration dampers and if you hard glue it will most certainly go bad. No reason...Muphy's law. I have had many go bad over the years....always easily removed.

The other reason for removal is it is much cheaper to buy new gears if they strip or wear than to buy a new servo.
...easy to remove for servicing, testing, looksy at gear teeth, etc.
My 2 cents.