Of course single-page apps generally require far more development than multi-page. Of course they require more state, more testing, are slower to load, etc.
But they also do a million things multipage "apps" can't and, and therefore have the potential to provide a vastly better user experience at the end of the day.
In the end it's same tradeoff as literally every other business decision: will the resulting benefits be greater than the costs they incur?
My dentist doesn't need a single-page app for their site. Anything complex enough to intuitively be called an "app"... there's a good chance it does.