Most airlines never give the average flyer the reason for most delays, but they report them. If you use (the paid service) ExpertFlyer, you can usually look up the stated reason (in airline code that you have know how to decipher) for a particular delay. I've seen numerous threads in the AA forum over the years where somebody would ask about the reason for a particular delay (by flight number and date) and then someone would post the info from ExpertFlyer and someone (that person or someone else) would then decode it into plain English.

I don't know if there's a free service to look up flight status notes for Southwest or not, and I don't know if there's a guide out there to decoding such coded notes or not.

To me, that's sort of analagous to how airlines don't even tell the average person whether there's 7 or less seats in a cabin (or in a specific fare code) left for sale, but that information is out there too. See this recent thread: