In addition to loud bikes, the problem is also the constant wind noise. Whether on the track or sport-touring, earplugs help also with fatigue. Not to mention protecting your hearing. Wear them! I wish I had when I was younger, all those years of motorcycling and lawn mowing without plugs...I do have some hearing loss. I'm now preventing it from getting worse!
I like the Howard Leight Laser Lite. I have small ear canals and they fit the best. I've tried many other types, including custom, nothing fits, it's frustrating, as I'd like to have options other than foam. But, the Laser Lites work well for me.