RSUs, when vesting on a regular schedule, are a form of salary. When I consider how much I "make" per year, in order to compare to other offers/companies, I add my yearly wage with the RSUs that will vest in the next year at current market prices. The sum is my real wage.
Could the stock suddenly go up, meaning my RSUs are worth so much more? Yes. It could also go down. But short of my having/using better information than the market has, the going rate of the stock price is probably a good measure of what the stock will be worth in the near future.
Of course, it's always better to have been hired 10 years ago when you could get more stock at lower strike prices anyway.
As a new grad you might see $5-10k in extra annual compensation coming from vesting RSUs (i.e. in addition to your salary and cash bonus). But RSU grants start to stack. Say your grants start vesting after 1 year at 25% per year. Year by year you might see:
Year 1: $40k/4 = $10k vest, new $10k grant (also vesting over 4 years)
Year 2: $40k/4 + $10k/4 = $12.5k vest, new $15k grant
Year 3: $40k/4 + $10k/4 + $15k/4 = $16.25k vest, new $25k grant
Year 4: $40k/4 + $10k/4 + $15k/4 + $25k/4 = $22.5k vest, new $35k grant
Year 5: $10k/4 + $15k/4 + $25k/4 + $35k/4 = $21k vest, new $40k grant
At year 5 you've seen $82.25k worth of stock vest (assuming a flat share price). Which leaves you with $82.75k left to vest.
Now you're tired of working at BigTechCo #1 and get an offer from their competitor, BigTechCo #2. You know how this works, so you tell them you've got $83k in RSUs. To make it worth your while, they offer you $160k of their own RSUs vesting on a similar schedule. You're an experienced, senior hire at this point so your RSU grants are larger, but maybe because you're a new hire who doesn't know the ropes your first couple of years at BigTechCo #2 show respectable but not explosive growth:
Year 6: $160k/4 = $40k vest, new $30k grant
Year 7: $160k/4 + $30k/4 = $47.5k vest, new $50k grant
Then you interview again and move to BigTechCo #3. Or back to BigTechCo #1. Or you tell BigTechCo #2 you're out and they give you a retention offer. Or you get a big promotion. Either way, the RSU grants add up. All the while you've been pulling in a respectable base salary, raises, and cash bonuses. And maybe, if you're lucky, your company's stock price has gone up too.
Or you realize your gross income of $200-300k in the Bay Area earns you the ability to buy property, which means you pick 2-3 of the following outcomes: [1] small and/or shitty house [2] 2-3 hour daily commute [3] overextended and house poor. So you move to the midwest and buy a palace.
There are employees at Google with hundred million dollar stock packages, but those obviously aren't bottom-of-the-org-chart drones.
You can either work hard for a lifetime single-company career and get there in 10-30 years, or you can try to hack your way upwards with startups and get acquired by the same company. (or, the even more daring option—create something of value as a startup and get your own team to help grow it.)
It's often not talked about directly, but established tech companies (not "acqui-hire startup flavor of the month") routinely create hundreds of new millionaires every year. It's one of those weird worst best kept secrets. People don't like to talk about their net worth when it comes from steady work. People tend to only brag when it comes to media popularized lottery/startup windfalls.
Imagine even starting at Apple ten years ago before their stock went all rocket ship. Just by taking your standard options blocks and not getting fired, you'd be extremely well off today without overly exerting yourself (if not overly exerting yourself is even possible at Apple).