OK, let me address your point then:

Phone screening is skipped for most candidates, but for the few that we do want to screen it is mandatory to continue. Since this post is from potential employee perspective I should have used "extra" instead of "optional".

1. For about 90% of candidates our interview process has two rounds: skill evaluation by a senior employee or employees (e.g. a technical interview for software devs) that doubles as "vibe check" followed by 2nd round with a manager that is more focused on culture fit, making sure both sides have matching expectation and ends with compensation negotiation.
2. For about 10% of candidates who don't come with a recommendation from a current employee or from someone in our network, or from one of the recruiters we trust and doesn't have something else backing claims in their resume there is a quick phone screening before all that - just to filter out resumes that are full of BS.
3. VP and up recruitment is more complex, but that is to be expected and I doubt anyone has a problem with that.

We manage to get a candidate from first round to offer/rejection in less than a week most of the time (2 if there is a screen) and have both high long term employee retention and very low percentage of hires who don't work out.

I suspect that as company grows (we're closing on 100 employees) and recruitment moves further and further away from "the trenches" and people doing the hiring are less and less capable of judging candidate competence managers start adding more rounds hoping they will filter out the ones that don't meet the requirements.