  It is well known that at linear e^+e^-(e^-e^-) colliders using laser
backscattering one can obtain colliding gamma-gamma, gamma-electron beams with
energy and luminosity comparable to those in e^+e^- collisions. In this paper,
it is explained why this can not be done at high energy muon colliders. Due to
several physics reasons the gamma-gamma luminosity is suppressed here by a
factor of 10^{14} ! Another option -- gamma's from a linear collider and muons
from a muon collider -- is also discussed (and has no sense either). Of course,
one can study gamma^*-muon and gamma^*-gamma^* interactions at muon colliders
in collisions with virtual photons as it is done now at e^+e^- storage rings.
Muon-proton colliders are attractive only if the proton beam is cooled and has
the same parameters as the muon beam, in which case
  L_{\mu p} \sim L_{\mu\mu}.
