Not to turn this into yet another BC debate, but nobody "suddenly" stopped doing backwards compatibility.
360 didn't have full BC with XBOX.
Most PS3s didn't have full BC with PS2. In fact Sony has only ever done full BC with PSX games.
Nintendo only implemented BC with GCN > Wii, and then Wii > Wii U. Handheld fared better with Gameboy all the way through to DS Lite, and then DS > 3DS.
BC is not a thing that we've consistently had, and it's not something that suddenly stopped. Sometimes it just isn't cost effective to develop hardware that supports backwards compatibility; it can drive up the hardware costs and/or put limitations on innovation and architecture.
I'm fairly certain that if they could do it in an easy, cost-effective way, Nintendo, Sony, and Microsoft would all love to put BC into their systems, because having that preexisting library is obviously very valuable, but leaving out BC is sacrifice that the console makers are willing to make in order to push their system specs higher. I'm not saying this is a good or bad thing, but it's a consideration that the console makers take into account.