Late stage startups have to offer RSUs, as the equivalent option package becomes extremely unattractive if you depart before the company is public.

Imagine, for example, an initial option grant of 180K shares at $2.00, which expire 90 days after you leave. Then fast forward two years: The valuations have doubled every year, and half are vested, so you have 90k options priced at $2, but that last valuation puts at $8 each. Sounds like you have a lot of potential money right? Maybe, but not if you leave. If the company isn't public, you either have to rely on some secondary market that might be really shady, or have to hold your shares until IPO. To do so, you need to spend $180K, and prepare for an AMT tax hit of, roughly, 28% of the gains. 90k shares, with $6 a a share paper gains, means $135k in taxes that year.

So barring that secondary market for the shares, we are talking about spending $300k exercising the options. Few people can, or are willing, to put that much money in, even if on paper they are up hundreds of thousands of dollars.

RSUs will demand action at IPO, as you can't delay the exercise forever, but it's far better than, in practice, letting a majority of options lapse, even when you are pretty sure they'll be deep in the money at IPO.

RSUs are common in late stage startups. The share price at the time of grant is calculated based on an estimated valuation. If I remember correctly, in the year or two leading up to IPO, Uber issued RSUs to employees at a valuation of $49/share so the IPO price of $45 was already below grant price for many that joined late.

Non listed companies do give RSUs. For example: Stripe

I got an RSU offer from Pinterest a couple years back when they were private, though I turned it down.

Yet they are quite common in late stage pre-ipo companies bc few will take their options