>These days, where is the lock-in?

Photos, apps purchased, and iMessage are overwhelmingly the reasons I don't see people switch. All their kids photos, etc, are stored away and they'd have to figure out how to nicely export them. iMessage is seemless for them across devices while an alternative like Hangouts doesn't have the market penetration—it isn't ubiquitously used even among just Android users. Apps purchased I added to the list because often people don't think about it, but if you mention "re-buying all your apps" you see the frown appear on their face.