[danpalmer]

If a stock sees explosive growth, the stock you were granted before the growth that has now vested might be worth far more than the stock you were granted after the growth.

Except at the very beginning of a company when the valuation is entirely meaningless, companies figure out the dollar amount they're going to grant, and convert that into a number of shares. This means post-growth you're getting much less. That leads to the balance shifting. Would you stick around for next year's $200k if you've already got $10m in the bank, probably not.