What emergency has befallen you in the past to suggest that carrying a phoneis an immediate requirement?
What emergency is bad enough that you think you'll need to call someone if you only a few Km from home
Are you running so far into the wilderness ( difficult in the UK) that you won't be stumbled across by a passing pedestrian, cyclist or motorist?
We've been sort of programmed into taking a phone everywhere "just in case" when in reality you don't really need to, and its quite nice to be away from it ( technology, modern life, pressure etc etc)
I run in the evening often just for the sake of running not measuring time or distance but just on whether I'm "done" it may appear a bit "zen bollocky wankshite" but it does for me