Video editing is not the only situation 17" laptop was/is used (on location is a big one). The 17" laptop was the standard of the recording industry. Logic (or other DAW's) is simply to difficult to work on a 15" retina screen (live mobile situations). Many people in the recording industry would have bought a new laptop (even though the market is small). It is sad that people want to belittle those of us who wanted and were willing to pay for the extra's that came on a 17".
I personally also preferred the 17", but the published figures from last year were that the 17" accounted for only 3% of MBP sales. Obviously, the number was small. And of those, some fraction will undoubtedly have accepted the 15" rMBP instead.
It raises the question of how large a niche must be to be viable. Apple obviously decided that the number of people who wanted a 17" was too small to justify.
I'm disappointed, but complaining isn't going to change anything.