I am troubled too but here's why I think this makes sense.
Phones will continue to get thinner and thinner. Apple have looked ahead and said, in the future when this thing gets thin enough there won't be any space for any adapters. The main competitor for use of the Lightning port is charging (as we can see from all the comments), but what if come iPhone 8 they will introduced simple wireless charging. Suddenly the need for any port then would come into question and pave the way for a significant further reductions in phone thickness.
Phones will continue to get thinner and thinner. Apple have looked ahead and said, in the future when this thing gets thin enough there won't be any space for any adapters. The main competitor for use of the Lightning port is charging (as we can see from all the comments), but what if come iPhone 8 they will introduced simple wireless charging. Suddenly the need for any port then would come into question and pave the way for a significant further reductions in phone thickness.