Webpages appear instantly in browsers, so people wonder why archiving took dozens of seconds, sometimes 3-5 minutes.
There are many reasons:
1. The instantly loaded page might have nothing but “loading” spinner, so there are intentional delays.
2. Webpage might have pictures loaded lazily, only when then user scrolls page down. The archiver scrolls the page here and there to load those image, even if the page lacks those lazy elements: it just has no idea so it makes a pessimistic assumption.
3. Webpage might have have analytic scripts which invisibly work in the background. The page looks loaded if you look at the screen, but it is still loading if you look at networks events. It make difficult to detect the moment when the page loading is completed. Even more, there are pages which do not stop loading at all (news feeds, stock market charts, …)
4. Archiving process has more steps than just load a page. It is better to compare with loading a page and then send it to paper printer.