[JonFish85]

"the main ones you care about are: revenue, expenses, total burn and cash in the bank"

That's part of it, but not all of it. Total number of outstanding shares (including warrantable shares!) can change the complexion of things a lot. And then there's the question of preference -- deals that a company made years ago can make for a big difference in share value.

Unless a company has an incredibly clean cap table, a rank-and-file employee will never really know how much their shares are worth until they are either worthless, or have a cash-in-hand buyer. What you're talking about is the general case of "things are moving in a pretty good direction", and that's important. But to really gauge value of a stock option is much, much more complex (and is constantly changing!). Even if an employee were able to come to a reasonable estimate of common stock value, one bad month can wipe that away (an emergency $5m round to make payroll? a loan backed by stock? a long-term lease backed by stock?).