Quite the opposite, normal is the “poor man’s raid”. Technically LFR is, but I don’t even count LFR as raiding, it’s tourist mode to see content.
Multiple difficulties in theory are supposed to be there to allow people to experience the content at a difficulty they are comfortable with. However, the problem is once people clear content on one difficulty, doing it again with just harder mechanics isn’t that appealing. Unfortunately when we’ve tried to make content only in the hard mode idea, you had people screaming that they couldn’t complete content they paid “15 dollars a month” for and such.