Takuan and Rand long ago discovered the basic problem- having the skills is one thing, but where do you start? What can you offer anyone? These organisations are already led; you won't work FOR them, you can kill their leaders but then they won't work for you, and then you have a new set of enemies.
Without anything to offer to deal with people, you are powerless and impotent.
And now, worse- all those organisations do work inside the Republic. By associating with you, they will attract the attentions of the Bureau.
Basically no-one will touch you with a barge pole. The Bureau has shut you out.
I would think that a Dark Sider would be worried that if he/she sought out an Apprentice, (and found one - or more than one - and trained him/her/them), that the Apprentice(s) would turn on the Master.
This has been the case of many conflicts, (EU), amongst the Sith and the Dark Jedi. It was even insinuated with the "Rule of Two". Darth Plageuis, (if he existed), was obviously not "wise" enough to see that his Apprentice, (again, insinuated as being Darth Sidious/Palpatine), would kill him.
In other words, I'd think one asscociated with the Dark Side of the Force would be worried that any Apprentice or Apprentices would make a mad-grab for their power, and thus not take on the risk of training one, or more.