I've been asked why I buy monthly comics instead of waiting for the collected books. The trade paperback versions are cheaper, and more easily stored on a bookshelf.
Besides the obvious reasons of impatience and wanting to be able to surf the internet without being 'spoiled', there's something else I like about monthlies that you don't get in books.
Yeah, I know - it's a little odd to like something most people find really annoying. Not too long ago readers were complaining to comic publishers about the amount of adverts filling the pages of comics.
It's not actually the new adverts that I like so much. It's picking up an old comic from years ago and seeing the adverts in those. You get an idea of the age the comic was written in with those adverts, and the types of products and services shown. It's almost like background reading. It shows, in a limited form, what was happening in the world while the author was writing his story. It's not something that exists in any other form of entertainment. When you watch a film, for example, you don't get a quick newsreel of world events from the time.
(Of course these days you can get x minutes of rubbish before the start of a DVD, but that's more annoying than anything else.)
Part of the joy of reading older comics is seeing these ads, and the nostalgia that comes. True, more recent comics adverts aren't as 'good' as the ones for x-ray specs or beefing up your puny body, but who knows - maybe in a few years all the car and computer game ads will be equally as entertaining. They certainly speak volumes for society today.
A quick googling revealed this site - Comic Book Ads - which contains loads of adverts from old comics. If you're interested, I suggest you check it out. Or - even better - pick up an old comic and have a flip through.