They only don't care because they don't have to. If they hadn't had a virtual monopoly on PC processors there's no way they so casually could shut out their entire existing market with repeated new platforms/sockets that bring only minimal (or even no) improvements.Intel is opportunist, they won't care about breaking compatibility
This may change in the future as stationary computers are being increasingly encroached upon by mobile platforms. CPU sockets may in fact not even survive the end of this decade.