You know what, I will take the bait on this one.
Allow me to enlighten you better on Runes. Runes are there to create a means of randomizing every champions base stats at the beginning of the game. Why? to put it simply, If they were not there it would be to easy to dominate an opponent simply by choosing a counter to their champion. That is when runes become most effective, if someone counterpicks you and you came prepared with a runepage that helps you in that situation, your opponent will be less likely to destroy you and you have a better chance of coming out even or ahead. That is all because those stats can literally be the difference between life an death early on.
Without any runes everything could be straight calculated out since every champion has set stats that grow a set way as they level. There is no variance, the champion will always have the same base stats and they will always grow in the exact same way. Runes change all that though creating an element of customization. If you favor using a champions abilities over basic attacks, maybe cooldown reduction is the best choice for you. You want to hit like a truck at level one? smack that runepage full of all AD or all AP and watch your opponents WTF as you bash their face in. Runes help keep snowballing down at early levels and provide options to help boost the weak points of a champion early on and sometimes later as well.
You idea that every champion uses the exact same runes aside from marks and quintessences is so horrifically wrong it is disgusting. While extremely basic rune pages like ad marks/quints with armor seals and mr glyphs (or Magic pen marks and ap quints) might seem good and work pretty much across the board there will always be a better optimization. Take vladimir for instance, Giving vlad a basic ap runepage would be a complete waste when you could cater to his passive and further boost his stats with hp seals and ap glyphs. That goes for almost every other champ in the game as well. I personally do not have a single basic rune page. all of mine are catered to the champions I like to play and I have found that more often than not they work well in some way with many other champs as well. Sometimes there might be a more optimal page but when it is a champ I do not often play it is not that big a deal to me. Keep in mind I have played this game for many years and have accumulated enough IP to buy 20 runepages and all the runes. I know not everyone has that privilege, but in the same sense... I worked a long time to get to this point and to have that given for free to everyone else would not be cool in my book.
As for your final example, sure you can farm the IP on a different champ than the one you intend to make the page for... but if you have the audacity to take that champ in to ranked to try them for the first time with that runepage... You should be backhanded until the correct amount of sense is knocked into you. I cant even explain how many shades of stupid that would be, and whats sad is you probably do it on a regular basis.