Does anyone ever explain why no one in the south cares about the Wall anymore?

According to this answer, The Night's Watch gets it's funding from The Gift, which is comprised of taxes taken from towns and villages near the Wall, I always assumed they were funded directly by Winterfell or perhaps even all of the kingdoms contributed in some way, a collective Wall Tax or some such.

If the Wall is there to keep Wildings out, and everyone knows the Wildlings are behind the Wall, in fact the Wildlings are constantly rading south of the Wall, which is why there is no one left for the Night's Watch to tax, why then does no one fund it?

If the Wildlings overrun the Wall, it's bad news for everyone in the south.

I've read the books and seen the shows but I can't remember if anyone ever explains why no one funds the Wall.

Is there ever a reason given?

It's pretty important but no one seems to care about it.