All points seem very valid.
A cause for this I believe is that of STUDENT LOANS. Before they came into being on the scale they are here it was more a case of having to go out and work to fund all your flying - Requiring a greater desire to persuing an aviation carrer thus providing an excellent 'filter' for people trying to earn that CPL or C-Cat/Grade 3 licence.
Strongly agree with the supervision thought - Ive seen it work well for new instructors when done right.
Cypher - I heard a year or two back such restrictions were being put on the drawing board (for C-Cats under supervision anyway) - I assume it was either just a rumor or is still is the process.