But you still have to carry two phones, or using work phone during personal time (as part of on-call). How is this better than just having PagerDuty/Incident.i

But you still have to carry two phones, or using work phone during personal time (as part of on-call). How is this better than just having PagerDuty/Incident.io/whatever and receiving pings there? You are disrupting your time anyway, but having an extra phone for that seems redundant.