Benm,
It does depends on the application, if IR leakage doesn't matter in a final product, filtering may be too expensive, or just not needed.
But in for example a lab, the IR can be very irritating because ccd camera's still pick it up. And there are enough applications where the IR would disturb measurements or worse.
When working with the green, you get protection for the green. Unless the IR output is listed on the laser itself, nothing warns the end user that his protection against green isn't going to save his eyes.
Filters getting loose is bad quality, a lasers that falls apart that easy won't live long anyway. Looking deliberate into a laser is stupid, but it should be possible for at least 10 seconds, as good safety eyewear protects that long against a direct hit, which would equal just looking into the laser.
But I'm curious, how much IR comes out of the different commercial units? And where would they be used for? I'm not that experienced with a lot of different lasers, most of my experience comes from the university lab.