[Bob]

He doesn’t look like an especially small guy, nor does the girl look particularly big. Why in hell wouldn’t he just pick her up?

[BenLurkin]

I'm guessing that his elevated consciousness told him that it would be wrong. Something about rejecting outdated gender models. He may have been concerned that it would be harmful to his girls psyche if she witnessed him exhibiting offensive “macho” behavior.

Or maybe he has a bad back.....