Will you get on a flight which runs an OS you know you used on your laptop and gave you a screen of death in your favorite color? Think about it.

No coder is perfect. Far, far, far from it really. You need testing, and testers often bring in perspective (also known as use cases) which the developers were missing.

Do a search on the most famous software bugs on Google to know what I mean.

And at the college level, get some read on test-driven development, unit testing and agile practices to know where things are right now.