Let's say you're granted about a year's salary in shares when you first join so you've vested $100K for a round number. When you leave that equity is worth $1 million. Now, you have to come to the table with the $100K to exercise and probably another $200K to pay the tax man. If the company goes belly up, you lose $100K outright and are stuck with a $200K tax credit that you get back in $3K per year deductions for the rest of your life.
Or, you could have exercised the shares as you vested and paid a bit less in tax with the lower 409A valuation..but you're still maybe looking at a $100K total tax bill.
Do you take the risk or not? Or do you end up locked in for a few more years of handcuffs while waiting it out?
It'd be really hard for me at least to walk away from this situation with nothing..so then I have to value the equity as something. And if I want to treat it as 0 it'd be really tempting to wait a few years and see..which again means the equity is worth something to me.