…people blip because it allows you to downshift MUCH faster. The reason is that you don’t have to spend any time finding the right engine rev level. You just rev it and dump the clutch. Here’s proof of how fast you can downshift smoothly (notice that the camera doesn’t shake at ALL) when blipping. Pay attention to Rossi’s neon yellow glove on the clutch starting around 00:26 or so. Each pull is a downshift. Yes. That fast:
The Video (MotoGP has disabled embedding)
You say it’s harder to achieve a smooth downshift, and while it’s true that it’s harder in the sense of taking more practice, once you’ve figured it out, it’s actually easier because it’s totally mechanical. Again, notice that the bike doesn’t shake at all as Valentino shifts down. Part of the reason is that you wait for the engine to hit the top of the rev and start spinning back down before you dump the clutch. That way both the engine and the bike are slowing and some of whatever inevitable speed differential gets “absorbed.” The other reason is that the if you’re in one gear, there aren’t too many possibilities for how hard you should rev it to drop down a gear. You figure out how hard you need to rev in a particular situation and that’s that. In a way, you’re just “rev matching” REALLY fast.
So why would you need to go that fast? The obvious answer is “for the track,” but that answer is a bit naive. Anybody who thinks of a riding skill as wasted on street riding should think twice. I could give you lots of little examples where this would come in handy, but here’s the over-arching principle: combined with simultaneous braking, blipping allows you to stop or slow down quickly, ending up in gear with the clutch out when and if you need to get back on the gas. This can save your neck, and has saved mine more than once.