Say I want to set up a reminder to pick up some dish soap next time I'm near my neighborhood grocery store. I could open the "Reminders" app and try to do it, but that only works if the store is in my address book for some reason or I know the address. Otherwise I have to search for the grocery store in Safari or Maps, copy the address and paste it into the "address" field for that reminder.
So I've learned my lesson - next time I open the Apple Maps app and search for my neighborhood grocery store, thinking I'll add a reminder from there. But you can't.
Software is super hard, and I get that, and I still love and use geofenced reminders every day. But this particular set of interactions is too complicated for, say, my mom - who just got her first iPhone (and smartphone) - to use, which makes it kind of a problem.
Arbitrary locations aren't easy, but the fixed "work" and "home" ones are... and for the purposes of this discussion, they all use the same battery life.
Those location aware reminders are not so helpfull imho, if I am in a hurry switching trains, or afraid that there might be a traffic jam, or unsure at which gate my plane departs. Must take hours to prepare those with location aware reminders esp. in such huge areas like airports.