Yeah but not all engineers who join Google stay in Google forever.
The ones who eventually leave and start their own company bring with them whatever parts of the Google culture that they felt were valuable: maybe it's the data-driven, engineer focused management style, maybe it's the code review and use of real computer science in the creation of software, maybe it's the free food rule.
They also leave after meeting a lot of smart people and making a lot more connections that could potentially help them in the future.
The ones who eventually leave and start their own company bring with them whatever parts of the Google culture that they felt were valuable: maybe it's the data-driven, engineer focused management style, maybe it's the code review and use of real computer science in the creation of software, maybe it's the free food rule.
They also leave after meeting a lot of smart people and making a lot more connections that could potentially help them in the future.