it is, of course, complete BS that this is the norm.
however, be aware that you can negotiate for early exercise or 10 year expiration prior to joining. even if the startup has never done anything like that prior, they will make it happen if they really want to hire you.
I have a deep network of friends in Silicon Valley who jump from startup to startup, and I tried to educate them when it comes to this topic, telling them to absolutely make sure the equity conditions were reasonable. None of them has ever managed to change those on an offer, it always comes back as "It's the standard contract!", and they are in general strong performers.
In my experience, unless you are really an insanely high quality and senior hire, for a standard software engineer they're not going to do anything like that, since they have other candidates at the door who won't mention the equity pieces, you can't fight the system too easily.
I've personally been in an interview feedback loop, back when I was at a startup, where one of the founders (who was an interviewer) said: "This guy is technically really good, but asked too much about the details of the equity compensation, I think he might not be focused enough on our mission, let's pass".
perhaps im extrapolating too much based on my own two data points. im just a normal senior eng, but have been able to get my last two offers modified (once with early exercise, once with 10 year expiration).
The alternative to making sure the equity conditions are reasonable is to value them at $0 when deciding whether the compensation package is good enough to get you to join.
But how does that solve the problem I had, exactly? If you later find out that your equity is on paper worth a lot of money, and you want to pursue other opportunities, do you just leave the potential money behind because of an assumption you made several years before which turned out to be statistically much more unlikely than the current expected outcome?
When your startup is at series E and your options on paper are valued 7 figures and all the investment rounds were raised with clean terms (see linked post), I find it debatable to still hold on to the assumption that they should be valued at $0, like they were at Seed/Series A when you joined, and so be willing to walk away from them rather than dealing with painful vesting/exercising conditions that were initially set in your contact, no?
When you play the lottery, you expect $0 back, but you also expect that in the rare case you win you won't have to pay taxes on your win years before being able to get the prize, otherwise you just wouldn't play at all.
however, be aware that you can negotiate for early exercise or 10 year expiration prior to joining. even if the startup has never done anything like that prior, they will make it happen if they really want to hire you.