In other parts of the world, you seldom see wheelchair pax at airports, but in North America, it seems that every time I enter the jetbridge after a flight, there are like twenty wheelchairs waiting for pax.

My guess here is you experienced TAP's way to discourage pax from requesting those wheelchairs, as it is expensive for the airline. Just like some airlines tend to make their special meals as terrible as possible, so pax won't order them again.