The National Venture Capital Association (NVCA) benchmarks[1] show that over 95% of term sheets across all funding rounds include a 1x liquidation preference.
[1]https://nvca.org/model-legal-documents/ (it's in the Enhanced Model Term Sheet v2.0)
The second problem is that companies are never transparent about any of these things. If you ask, you get funny looks or continued evasiveness, and candidates are left with only part of the full picture anyways. From other comments here it seems that even if you run through a checklist of questions, the company’s structure could drastically change in a subsequent funding round of some such event. And if that’s the case, does knowing the current state of affairs matter at all?
You're right that employees with options don't get enough information to understand the value and potential value and mechanisms of their options in private companies. That's what I was driving at (poorly) in a separate comment.
3x would mean something is wrong with the company.
The problem is that if a company has a lot of shares outstanding with a high liquidation preference then outcomes that look like success to employees or founders may not result in those employees making much money, and the employees generally don’t know the relationship between how much the company is sold for and how much they get paid because it is confidential to the senior executives or investors.