That's curious, I've never met a Tesla owner who told me they had a subscription to another charging network. Perhaps this is a more local phenomena.
It would be nice to hear from others. You can count me as a Tesla owner who has never used a non-Tesla charger.
Many ChargePoint chargers are free, but you need a ChargePoint account to access them (RFID card or app). They are located in a number of publicly accessible parking lots. I am a Tesla owner who had used them a number of times and never had to pay.