"To compensate for slow page load" is probably my main use (still rare), and, hey, sometimes you've got slow page load.
Another reason might be to avoid losing state on the underlying page.
If you have a "SPA" style app, it might obviate both of these reasons. In an SPA app (ideally one with good URL and back button behavior of course) the difference between a modal window and a separate page perhaps becomes _only_ one of UX, which presentation is better?
But in a more traditional server-side-rendered app with minimal UI-focused JS, other considerations still exist which are legitimate, it seems to me.
Another reason might be to avoid losing state on the underlying page.
If you have a "SPA" style app, it might obviate both of these reasons. In an SPA app (ideally one with good URL and back button behavior of course) the difference between a modal window and a separate page perhaps becomes _only_ one of UX, which presentation is better?
But in a more traditional server-side-rendered app with minimal UI-focused JS, other considerations still exist which are legitimate, it seems to me.