Stock options are valuable compensation for startup employees. The high potential upside of these options motivates employees to turn down larger salaries at bigger companies and work at startups. It seems obvious, then, to expect that employees should own their vested options outright, even if they leave the company. Stock options are compensation for work that’s already been done. Returning them to the company when you leave would be inequitable.
It’s kinda crazy how high Apple’s stock is right now (currently $339). I wish I had invested more in it when it was only $90. I only considered buying their stock at the time because I believed in what they were doing, and didn’t really care about dividends or stock price fluctuations. I recently took stock of what I spend my money on and realized that Netflix is another company that I believe in, and would consider investing in without doing any research.