Consider the space we are in to be on the outer edges of star systems. Jump points occur here. They are therefore position of importance – trade hubs, strategic bases and places of manufacture and industry. Travel to planets in system the can take a day, sometimes several, sometimes up to a week depending on the position of the planet and the cruising speed of the ship. We remain out there because that is where we are needed, system ships and local defenders can fight if need be (though nothing should make it past us and the enemy would first need to secure the position to be able to strike further in system). We see the main star often (it is basically the skybox) but the planets being so small in comparison, we cannot see them.
Why do we never go? One TSN ship is a formidable asset. To have it withdraw in system would remove that asset from operation. We have repair and maintainence facilities, and established bases and HQ posts so TSN ships never need to visit a planet. It would be like bringing a satallite back to Earth to fix a faulty wire, just to have to launch it back up again.
I envision the blackholes as more like micro gravity wells. Of course, what is a blackhole if not a gravity well.
There is more indepth stuff, mostly available to the canon department at present and much is written out of character. Things are being developed and tweaked and finalised (hence it is not yet accessible to every – the intention being to avoid confusion or a change that results in conflicting ideas) but will hopefully be accessible to all at some point in the future.
It is fine to ask stuff if you want to find out though. An answer could be provided from what we have, or new canon written as a result of missing information.