I actually had meant to type "home & auto repair...". But anyway, IMO most of the value is learning what's going on in the car and the process of diagnosis. Many, many shops employ the "speculatively replace X and see if it fixes Y" iterative process, and being able to avoid that whole process is useful.

You are right, the cost savings on doing your own oil changes isn't particularly significant. Although it's also worth pointing out oil changes are the most commoditized, sometimes-loss-leader service in the business- if there's a cost savings to be had, it's in moderate repairs that are a little more involved but don't require lots of equipment. Replacing an oxygen sensor or alternator, for example.