I agree with you for the most part, but remember that the big 3 can be the key to people getting comfortable with the whole process. This will allow them to learn the technical side of the exchanges and be willing to branch out into the other alt coins. At the moment the big 3 are much easier to buy, store and feel comfortable. Finances are an emotional tool for most people, they need to move forward slowly while researching at first. Some will go through this process very fast, others will take more time.
RE: New to Cryptocurrency? Here are some helpful tips