Yes, they definitely should use something like that from the start, in my view. But I think they won't, because there is now a lot of evidence that this will result in a bunch of bad press, whereas just making it proprietary will go without comment.
What incentive do companies have to do this?
the best strategy is still to start out with something that's press-positive (Apache2) and switch to BSL/SSPL after funding is secured. bad press will happen, but at least later, after the good press phase.
Yeah, for things running server-side that could be used by Amazon and Microsoft, they should use SSPL from the start. In this case everything is clear and everybody knows what to expect. For regular users, there is absolutely zero difference between SSPL and OSI-certified licenses.