One thing I like to do is preview a link by Force clicking on it in my browser and scrolling through it–the preview window lets me scroll, but not interact with the page. For many sites this is quite convenient, because I can skim the page without being interrupted. But when modals pop up they cover the content and I can't read the page because I can't dismiss them! So if you're looking for another reason to drop modals, here's one.

Also, hilariously this website uncovers a bug in Safari where the cursor doesn't reset once you leave the page bounds, so I have a huge pixellated cursor hanging around until I click somewhere else :P