Not all ISP's are like that. MikroTik is used by many ISP's in Europe. Dominant? Not yet, but it's getting there! U.S. is not really popular these days, you know? Trust in the pesky, backdoored Cisco switches is at an all-time low, cost notwithstanding. This is pushing telcos to consider alternative architectures that do not require certain proprietary features pushed by the big-three switch and router manufacturers.

This is not rocket science.