The "trickle down" concept didn't work well with the economy, but it has long been used with spiritual learning, and seems to work very well.  The most advanced spiritual adepts learn from angels and adepts who have returned to the spiritual world.  They in turn teach the advanced students.  The advanced students teach the intermediate ones, and the intermediate teach the beginners.  This method is used for a number of reasons including:

1) The beginning student isn't ready to learn the most advanced concepts, so doesn't need a very advanced teacher

2) The most advanced spiritual teachers and adepts have important lessons to teach the advanced students and don't have a lot of time left to teach the basics to beginners.

Occasionally, the most advanced teachers will teach intermediate and beginning students, but when they do, they have to keep the teaching to those subjects that can be understood by all.

And, in case you're wondering, meditation is not an advanced spiritual teaching, taught by advanced spiritual adepts.  It's a very basic idea taught to beginners.  Once they learn it, they are expected to move on to higher teachings and techniques for spiritual development.