I have a friend, an engineer but not a programmer, who wrote a fortran program he's been using for decades to solve real problems.

But then recently he had to solve it for 10 different things instead of one. So he copy/pasted his calculations 10 times. He said the problem he was running into now was when he tweaked something, he had to change something in 10 places.

I think that's how normal people solve problems. They just bumble ahead doing what they know will work, but it's not pretty.