I consider carrying a little extra as an investment.

If something happens to my hiking partner because they are not as equipped as they "should" be, then it's going to fall to me to drag their butt out.

It's also a little cushion should Murphy chose to tag along (being the party pooper that he is).

There's a balance of course between me being the pack mule and the other person being responsible for his/herself.

I only hike with those I care about so the investment isn't a burden.