Comment by jesstaa

Compile time is a big deal when you have millions of lines of code that constantly change and very expensive devs that are spending large amounts of time waiting. The infrastructure Google uses to distribute and track builds across datacentres and the world to make compile time of large applications bearable isn't exactly trivial.

Optimal executables aren't that important most of the time. Hardware is cheaper than dev time and the gain of 'optimal' isn't much for the compile time trade off.