You would be surprised that most wifis out there still don't run on 5ghz. I mean what do you expect from non-technical people, wifi is just this white box that should work, if not turn off/on and then call support. Ie we (Switzerland) have both bands available from the router and till now even I didn't know that higher band is better for interference, and I am most technical in the family/friends circle.
5Ghz also has drawbacks. Routers support both, usually with an option to either combine them and handle the selection automagically or separate them. Parent is just wrong about routers having switched over completely - and thus the microwave can indeed still be a problem.
