Funcom have stated that they don't want every profession to be able to self-cast every nano, even at level 200.
Admittedly Traders and MPs can (and in both cases they can cast all their nanos very early) but that's mainly because they always have a buffing MP or Trader 'on hand' as it were.
Perhaps with hindsight they should have scaled up the trader and MP nano reqs to take into account the available buffs more (since both profs run out of new nanos very early), but I believe the nano designers made a conscious decision to make certain professions' nanos very difficult or impossible to self-cast at any level.