Ummm... "why?"
I don't know. It could be:
1) The perceived risk is greater on distant trips.
2) The actual risk is greater on distant trips.
3) The impact (either way) is greater on distant trips. See #4.
4) Readily-available amelioration is better near the home. (How DO you say "I need an aspirin tablet" in Serbo-Croat -- and for that matter how do you say, "If you understand Serbo-Croat please say "iess" and if you don't please say nothing" in Serbo-Croat? And if they speak Ferengi instead of Serbo-Croat, how will you know and does it matter?)
5) And with exceptions, the lucky ones among us don't travel a lot. (So I'm not lucky. Pray for me. *\;-)
If they speak Ferengi those aspirins will cost you a quarter bar of gold-pressed latinum apiece.
There's a pawn shop near here that trades in latinum. I saw it on their sign.