While it appears to be a no-brainer to add, there are a lot of units that can't spare the half ton without losing something important, like armor or ammo. Putting recon cameras on a scout unit makes perfect sense, but giving up half a ton of armor for it on a main battle tank or fire support vehicle would seem to be of dubious value.
Some of the hovers (Pegasus, Condor, J. Edgar, etc.) for instance, could probably spare the armor, because they're far more likely to die of motive criticals than by running out of armor, and they're fast enough to put the spotting equipment where it will be effective, and generally live to tell about it. Putting spotting gear on something that's more likely to hang back and provide fire support than to call for it seems counter-productive. Stripping a half ton of armor from almost any canon VTOL design, which is already likely to be heavily under-armored and minimally armed if it's got weapons at all (there are a few exceptions), would tend to leave it depressingly vulnerable to just about anything that hits it.
Basically, there's a definite place for it, but it's no universal solution for all of your targeting needs.