Because of the less enlightened places, it may be required.
Sadly, even that doesn’t always work. I was very unpleasantly surprised last year when we took a long vacation from Georgia, across I-40, then up through CO and UT to ID, and back through WY on the way home. I wasn’t at all surprised that we’d have to avoid IL to remain legal on the way back, and accepted the fact that NE was also off limits (home of Cabela’s, no less!). But I was totally surprised that we couldn’t legally enter NV or NM on the way out either. I did not expect western states to not honor a GA permit. So much for constitutional carry….