I remember back in the ancient days when there weren't really comic book shops to go to buy your books; you had to rely on the newsstands / local drug stores / etc. to get in stock and put them out on the spinner racks or wherever they were displayed. And even when comic book shops were more the default place to go for most comic books, they weren't originally written specifically for trade paper back collections; only some stories achieved that distinction, not practically everything.
It's nice to have the option of later buying stuff in collected editions, but it has taken a toll on how many stories are written these days.