Why bother buy rune pages since all runes are free and can be changed in the champion selection?

Why bother to put the entirety of your post in the title, and then say "Title." as the body of your post? You're doing it backward.

There is so reason to buy extra pages anymore. I have literally just used one and edited on the fly as needed.

Probably because people have their own champion they like a set on and then have at least 1 page for theorycraft. Or you know too lazy to constantly switch runes around.

It amuses me how theres a bunch of posts talking about how we need more rune pages, and simultaneously others posting about how more is pointless.

People are lazy and/or don't like thinking on the spot, so some people like to have pre-prepared rune pages for most situations they're prone to encounter.

I play a lot of aram, so (having 20 pages from old runes) I'm inclined to have a page for every primary/secondary combination, so then I can just quickly tweak within those for a specific champion instead of needing to remake the entire page from scratch.

Others may play only a handful of champions, and want a page for each of them, and maybe a few situational pages for those champs as well. (Most champs have at least a couple viable rune pages too, so having different set ups for the different flavours of playstyle is nice as well.)

Certainly there will be people who only every use a single rune page though, much as there were people who only every used a single mastery page.

Most likely sheer laziness.

I don’t get all the bitching about having to buy rune pages. There’s plenty of time to fix up a rune page for a champion as needed.

Even though I had them beforehand, I don't like the thought of having to change my entire rune page every single game I play