The same gut reaction that causes you to go "ugh, crap code, I'm going to rewrite" is probably similar for the other developer, but with your rewritten version.

People tend to have an aversion to code they didn't write in general, and actually reading and understanding existing code tends to be a rare skill.

> Also, rewriting something is far easier than writing it from scratch.

Given the amount of times I see companies rewrite their product with half the features missing and more bugs than before, I'm not sure I agree with that.