Laser beams diverge. That is, the beam coming back would not be as intense as the one going out. The laser on your keyring diverges a lot, but even the best optics will have some divergence.
Also consider a weapon system covered in reflective material. Hard to keep clean in the field, and not very stealthy.
It seems directed energy weapons have some future, not as a final weapon making all others obsolete, but as yet another kind of weapon. Will they be the "nuke" of the century? Sounds like PR exaggeration.
Alternatively, if you detect that beam (like our laser guided weapons are capable of doing) you know there is a big fat airplane on the other end of it.