Originally Posted by MRT2

Yup, conditioning. I have considered switching out the gearing on my bike to get a lower than 1:1 gearing, but have resisted the temptation. If I can't get up a hill with 1:1 gearing, I need to work more on my conditioning. Most hybrids have a super low gear that should get even a moderately fit person up all but the steepest hills.