For at least some of the L7+ people I know who have left they weren't interested in growth (others I'm not certain). I know one person who left because they weren't able to get the VPs to greenlight their stuff and eventually got frustrated by it but I definitely know others who left because "continue to be a responsible steward for this large ecosystem that is important to Google's ongoing success" was no longer a viable path to sustained work (as opposed to promotion).