That's fine as long as startups don't sell you that the equity that's part of your compensation has any value. In other words, they pay you market-rate that big companies would in salary+liquid equity and/or you decide that whatever discount they offer is worth the difference in work environment.

...Which is not the case at Dropbox or any startup really.

They may have liquidity events even if they aren't going public.

I agree, if you're able and willing to pay market salaries rather than 80% of market plus some ephemeral equity that you've no realistic possibility of realizing value for...

But if there is no equity that is not a market salary anymore.

Apple/Google/Facebook/etc has market salary and equity (and/or bonus). So if you take away the equity the salary needs a significant bump to be comparable.

A startup with no plans for an exit seems to not be a good thing for employees.

No idea if this would work but I wonder if some kind of profit sharing plan would make more sense than equity for these cases.

That way people still get the big payoff but get to keep control of the place they like working at.