As I explain to my students, like four wheel drive, STOL is best used to get you out, rather than get you [further] in. STOL kit modifications are very common in Canada, and can be real life savers. But this is more the case in maneuvering safety than short takeoff and landing. Indeed, when one actually considers the ground roll distances required by many light aircraft, those distances are happily short. It is unlikely that one would find usable runways that short. So, "short" runways are commonly within the stated requirements of many light aircraft.
What I find troublesome, are "STOL" climbouts where there is no obstacle to clear, just for the sake of showing off. These eager pilots seem to overlook the fact that if you are climbing away at speeds in the STOL regime, an engine failure will leave the aircraft entirely unable to enter a safe glide before arriving back to the surface. Sometimes, this is operationally necessary, but not in the name of fun.
Similarly, if a STOL arrival is flown, the approach angle may be steep, and speeds slow. It will require extra skill and judgement to flare appropriately. Aircraft have come to grief, because the pilot simply did not arrest the descent prior to surface contact.
STOL type aircraft will be more safe to maneuver, allowing greater margins of safety in turns and increased G maneuvers, though again, if the pilot is in the habit of operating in that range anyway, the margin of safety is surrendered.
I would rather put a pilot in a plain Jane 172, and teach them to fly it with precision, than to put a pilot in a super STOL type, and try to teach them STOL skills. The 172 (or a number of other similar types) reward precise flying well.
Non standard landing surfaces are another story, but not so closely linked to STOL.