So if you consider getting all salary in cash and then buying GOOG (or any other stock) with it, you come off only a month or two late on the period for which you are holding the stock. And for that, you lose out on the diversity of the stock.
This also assumes that your GOOG stock starts vesting immediately and there is no cliff. Otherwise, you will be holding the stock for "cliff" period longer if you just get cash salary and buy the stock.
Disc: Googler but this comment doesn't have anything specifically to do with Google. Google is just an example here.
If you make 200k a year for 10 years, vs get no salary for a startup for 10 years and then its sold out for 2 million dollars, they are completely different tax conditions.
Im not an expert or have been through this, but if you sell 2 million dollars at 15% long term rate vs the 35~% + medicare of salary, the difference will be huge.