Perhaps you work in a different part of Google than I do, but I've been here for four years and I see many good engineers getting pushed into management roles to advance their careers. Their job title is still that of an engineer, but they end up with reports, schedules full of meetings and use Google Docs as their primary editor.

It seems that the ability to have an impact while writing code is quite limited in the industry, and the way to expand it is to take on leadership and management roles, even if you aren't technically moving onto the management ladder.