They're isolated because they're wrecks. A wrecked freighter in orbit of manhatten isn't going to be much use to anyone.

There are wrecks scattered throughout the various systems, typically in out of the way--and sometimes dangerous--places. You can, as you say, get equip,emt and sometimes goods from them by shooting them and tractoring. Using one relatively weak gun is a good idea: I've destroyed everything aboard a wreck by firing a salvo instead of being gentle.
But in addition to "mining" wrecks, there are a number of systems that have fields of resources you can get in similar fashion. Use the mining filter on your map to locate areas, go there and fire at the asteroids (ore) or ice chunks (water)or ship pieces (scrap metal)...whatever is in the area. Fire at the ones that, as they fly by, provoke a response from yur targetting reticule; the other stuff doesn't yield anything.
But not every blown up rock or whatever will provide something for you to tractor in...I spent about 20 minutes in Dresden shooting up all the passing "lava rocks", and got about 70 diamonds for my trouble. Takes patience, and trading's faster. Or running high reward missions. But mining is another role to play.

It's better to burn out than to fade away

Yeah, mining is ok since it's 100% profit, but it takes such a long time to get a full load that it isn't worth it in my opinion. It's just too boring to sit there shooting asteroids for a hour... Now ship wrecks are great because you can get some awesome weapons from them.

Well if you just happen to be in need of money,.. because you dont have it,... you can only take missions,... or you can mine,... the latter is less dangerous,...

OK, that's a good point. My problem there was that I was always on the bad side of the patrols flying around all the really good mining fields.