At least one source I've read says, beginning cyclists often want to use a very hard gear because they feel they ought to be working hard all the time. I must be an aberration, because I'm the opposite!
A hard gear in a low cadence makes me feel like I'm not working, precisely because my legs are moving so slowly. An easier gear with a rapid cadence feels like I'm working harder, even though I can actually be going slower than in hard gear/low cadence.
It's up to everyone to find the so-called "sweet spot"; the gear that's most efficient for the riding conditions at the moment. Since that can vary so much from one rider to the next, having a multi-geared bicycle is a huge help when it comes to endurance cycling and racing.