Because they're not--I love my Macs way more than I ever loved my PCs, but have a look at what OSX and/or Firefox does. The top browser popped into being above the menubar. On Macs, the only place you can drag windows from are the titlebars. Of course, if you can't reach the titlebars, the best you can do is force-quit (ctrl+alt+del for Windows folks) and restart the browser in hopes that it won't happen again. This isn't a huge deal these days--but in the days before session managers to remember your tabs, it really sucked. Nowadays it's just annoying as heck (not hell).
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