Background characters having a history is fine to me. Why not, they could be cool/interesting characters...
The problem is, that all of them seem to have had a connection to the original Star Wars Cast. That is just ridiculous. The SW universe is so much bigger than that and should provide many stories and characters that are independent from everyone that mattered in I-VI.
It made sense for a few storylines and the likes of new characters like Kyle Katarn, Thrawn and Mara Jade... but why try to retcon everyone to be an old friend or adversary to Han, Luke or someone else from the past?
Are there books out there that have the quality of the Thrawn trilogy and capture the essence of Star Wars, but have nothing to do with any of the old characters?