Um, no I don't see that as the reason. While runes can boost/enhance hero skills, I would not consider them an alternative or a substitute for gearing up or adding enchantment bonuses to your heroes.
PMtactics's announcement last December of v2.0 of the Rune system being in "active development" and they were "looking at a release in Jan/Feb" (referring to LAST freaking Jan/Feb...not the coming Jan/Feb) was highly and wildly over optimistic. No argument there. I also agree that waiting 10+ months for said rune system, or any rune system, to be released to servers 7 through 11 is just plain not cool.
However, I don't agree that the reason runes have not been released to newer servers is because of players spending real $ on gear and enchanting. Collecting enough runicite and sufficient numbers of runes to even start having a decent impact on any single hero is where the real $ signs would theoretically come into it. If a player was determined to really get runes going, they could drop a whole ton of real money on shrines alone. Then add in the option to pay for the runicite needed to get anywhere in the rune temple and that could really add up.