A collection is really all the crap you got and stuffed into a box and felt good that you had it. It isn't necessarily something you think about much or pull out very often. But it has a value, an ever accruing sentimental value.
What that does to the care with which you backboarded or plastic sheaved is for you to determine. But it it is good that there are nerds or geeks or whatever else they call the (inadvertent?) collector preserving these things for posterity.
One day a museum is going to pore over our quaint customs and researchers are going to seriously question our ways. We do it to previous generations so why should things be any different then. But that's no reason to trash our art or burst our bubble.
Comics are another artform, publication, pop culture item, work, product, item, reading matter, sequential narrative, that people like to collect. They've become moreso with a change in generational attitude (just chill, man) and the sophistication of the graphic art medium.
This applies to superhero sagas as much as prison camp dramas or densely realist vignettes. Fans have a say in whom they make their idols in the production department. That's if they aren't too busy drooling over the characters to pay the technicians sufficient mind.
Older stories are of interest for their very antiquity. Perhaps a pre-code appearance of a cherished character or the first use of the villain growing to an enormous size.
Fans who have been accumulating comic books will know the books to collect from a certain writer or artist. (I guess it would be possible to collect inkers, though probably not anyone else whose name appears in the credit of the comic itself, unless they also happen to be writers or artists as well).
Great storylines ensure that collectors take an interest in a certain company. It's more the publications they produce and the characters they feature, certainly, but a brand loyalty is engendered just as surely. It's Harvey league stuff sometimes but the collector market doesn't discriminate as online auctions have proven only too well.
What's the difference between a collectible and a collector's item? The first is more ostentatious in presenting itself as something you might want to keep - preferably in the box.
A collector's item often only becomes so over time, not just because of its increasing age, but because it is all the better for not being self-conscious. Those holograph covers and crossovers and extravaganzas and anniversary issues are all well and good, but there is an oversubscription from amateur collectors who don't realise these things can't be wholly engineered.
You can buy a series that begins again from number one if you want but I find the corners of comic collecting are where to find the still interesting stuff.