It IS worth $0 of real money. Future money / as risk? Sure, it's worth whatever the founder says. But in the end, equity doesn't pay the bills until I can cash out, so if you offer me 30K less than what I tell you my current salary is, I'm very, very, very unlikely to take it, because at the end of the day, I still have to pay my rent. My landlord won't except "Well, in a year, I get 25% of my stock options, and I can pay you then" as a rent check.
Your equity is worth $0 cash right now. It's not a replacement for salary, it's an incentive to do well. If we do well and if we successfully exit or get to the point where this sheet of monopoly money is exchanged for $X, then it can be a replacement for salary. Until that time, it's a risk and not a salary.
When it comes to salary, I need enough to be assured that I can pay my bills on time each month. Once you meet that minimum threshold, then we can start talking about equity. What you cannot do is say "Well, instead of 30K salary, we'll give you 0.5% of what we imagine our company is worth," which is only slightly better than saying "Instead of 30K salary, we'll give you monopoly money."
Furthermore, in some cases (including my own), people are already at jobs where stock has vested or the company has been acquired or IPO'd or is otherwise successful from an equity standpoint, and in those cases, your equity is worth even less, because I'd have to give up X percentage of my current salary AND my currently vesting stock (that may be worth real money) to work for your company where you may or may not get to the point where you're successful enough to pay out on stock.
The above is part of the reason why I said as a senior developer, you have to be either a founder (or C-level employee) or really, really, really, really, really believe in the product. Both are true in John Carmack's case, by the way. He fits my exceptions, so you kinda picked a poor example, there. :)
I get your point, though. I just happen to disagree with you.