Thing is, viccars are available year around, unlike the others.
Yus, that's probably their biggest advantage, but no one wants to lug around bags of those heavy things all year, waiting for spring to arrive. Though if someone did, they could probably trade them for a lot of money.
I believe that the original intent of the post was to not make "rare" components "common" but to at least have them someplace where a native barovian would actually have a chance to get them without having to make deals with filthy outlanders or do something as insanly stupid at crawling around in a barovian crypt.
But the two go together, because crypt herbs are inherently rarer than cave herbs. The fungus in the cave systems grow like weeds -- there are less crypt areas than cave areas by far, and there are less herb nodes per crypt area and players are frequently in them, keeping the places from resetting and spawning more mushrooms. The result is that you can farm the cave system mushrooms endlessly and get a practically unlimited supply. I'd say with all factors considered, you could gain a cave herb at about 6x the rate you could gain crypt herbs.
If crypt herbs started showing up also in caves, they would become the most common herbs of all time, which would be a rather huge change, considering it would only have happened because the rare Barovian herbalist that still somehow feared magic wanted to make a critical healing potion without having to hassle with mushroom trades.