The reason people make a big deal out of it, is that people are claiming that you can use CSS to separate semantic content from the presentation, when that is not 100% possible with current design of HTML/CSS. It's not really an argument about what floats were designed to do, it's a reaction to the purist argument that layout shouldn't be in the HTML. Perhaps that's a bit of straw man, since, as you say, it's obviously false. However, there is a bit of confusion out there resulting from people arguing HTML can be kinda like XML, and CSS can handle all of the layout. It's not a good position to argue, because HTML is a primarily a presentation language, in addition to offering a few opportunities to sneak in some semantic metadata.

At least people aren't using JS to move everything around on the page any more. That really sucked.