I see. For now, this may be country specific, so it all depends on where you are traveling. I looked at countries where I would possibly travel, and I'm covered: UK, Finland, Netherlands, Germany, France, Australia, New Zealand, and Japan all have carriers that use eSIMs, so a purchase from one of them (and even prepaid, if need be), and I'm set. I'd get a local number to that particular country, which would only be used if someone from that country would be calling me. Otherwise for anyone else who would call me from home (I'm on ATT as well), they would use FaceTime.
The problem crops up with those who want to keep their domestic phone number while traveling internationally. Using FaceTime and local carriers would be much cheaper than roaming and the convenience of keeping your ATT number.
BL.