It's not just the exercise price... it's the taxes on the illiquid gains that really fsck you! Eg. you're granted $100k in options over four years. You want to depart the company now, when the shares are worth 100x. You pay your $100k to the company to exercise, but now you also owe taxes on $9.9M in gains -- and you can't sell any of that stock to pay the $3.3M in taxes to the IRS.

With a 10-year option, hopefully the company gets (or can offer) some liquidity to help you pay the IRS when you exercise later.