So people have annoying habits, and it's whatever, because EVERYONE has them. But there are some annoying habits that are also slightly dangerous.
When I'm in the library, I'd really prefer for the guy at the next table to NOT be flicking his lighter on every five seconds. There are a few reasons:
1.) It makes just as annoying a sound as clicking your pen.
2.) There's FIRE involved.
I think the whole fire inside a building thing is the most important part. And yeah, it's not like it's actually likely for you to catch something on fire, but I was seeing a distinct possibility of lighting someone's clothes on fire as they walked by. That wouldn't have been good for mister group project boy, especially since I think his project was due at midnight.