As someone mainly working in open source land, I can't tell you how under-appreciated it is to be able to _look at what some piece of code does_ to shortcut troubleshooting.
So much corporate "software as a service" stuff is poorly and incorrectly documented, and you have to take wild guesses at what any of it actually does.
(I'm mostly griping again about Mailchimp today, which is terrible no-good awful software, but it applies to so many things.)