> eminently reasonable

Companies feel like they have no choice, for two reasons:

1. Jurisdictions where workers must give minimum notice periods before leaving their prior employer - the worker accepts a competing offer, gives notice, waits out the notice period, then starts. And many workers often ask for additional unpaid time between jobs before starting (since no vacation days have been accrued yet at the new job).

2. Hiring happens by committee. In most companies, job candidates must be interviewed by, at the absolute minimum, an HR screener, the hiring manager, and the hiring skip-level; and usually also by people who will be peer teammates, plus an HR "culture" interview. If you need to pass a committee of 3-6 people, interviews must be scheduled with each member of the committee; at one committee member per week, that is 3-6 weeks.

6 weeks (1.5 months) plus background checks plus getting pay packages approved plus 30 day notice periods plus two weeks unpaid vacation is, yes, a multiple month endeavor at minimum to fill a role. The only way to fill a role within a week is to grant full hiring autonomy to the hiring manager and only hire people who are currently unemployed (and therefore have no notice period or desire to take more unpaid time before starting), which in most companies beyond early startup size, is a complete non-starter.