Others … on the road
Other people (and there are lots of them) do the wrong thing because:
1. they CAN'T BE BOTHERED to do it right
2. they DON'T KNOW how to do it right
3. they're UNABLE to do it right
4. they MISJUDGED it
My job is to help you eliminate numbers 2, 4, 1, and (with lots of imaginative teaching) number 3. Whatever, don't be too harsh. "It takes all sorts to make a world", including us: that's The Honest Truth.
We all get tired from time to time ("1"), but hopefully not permanently lazy. "2" is the bread-&-butter of an instructor's daily work. "4" will usually come with practice, which builds up your experience of successful attempts and similar circumstances. "3" is more of a challenge to some: we all have limits to our ability, but few of us rely just on natural talent—we need to develop by hard work, too. Keeping 1-4 in mind helps us "absorb" others' mistakes, and be realistic about ourselves.