Well I'm kind of with you on that but I go hill walking and find the GPS in my mobile a bit questionable, well TBH I seldom use it now. There are a couple of issues. Compared with a dedicated GPS (basic Garmin, mono LCD screen, no maps) mobile is poorer on acquiring, retention and positional accuracy (also I suspect it's guilty of power consumption). Although in the mobile GPS does interact with apps if the apps need a data connection they don't work in remote, rural and mountainous areas. I can preload (detail 1:25k OS) maps to the mobile but its a nuisance, easy to forget and takes a big chunk of memory.
One problem with mobile phones is the obsession with small dimensions and weight whereas a dedicated GPS has plenty of space for good internal aerials, dedicated GPS hardware with well evolved software and replaceable batteries (AA in my Garmin so I get around 20 hours but I can take spares or buy them easily). Potential ways forward: a GPS with Bluetooth to communicate with the mobile or a nice chunky GPS with built in mobile (android).