Copy & Paste pulls in DimStyles that aren't even in the drawing I'm copying from?

This is getting extremely annoying. Anytime I copy and paste anything from one drawing to another (which I do often) it pulls in Layers, Dimstyles, and Blocks that aren't even in the drawing I am copying from?! I don't understand it. I have purged everything from each drawing prior to copying and pasting but after I paste, the items I just purged reappear. Can someone please help me with how to stop this from happening. It is getting extremely annoying to have to purge CERTAIN items from a drawing that I don't want. I can't even do a purge all because there are blocks that I have in my prototype that I want to keep but don't necessarily use all the time. SO FRUSTRATING! I would not say I am an advanced AutoCAD user but I am certainly not new as I have been using ACAD for about 10 years. I do not get into lisp commands, certain block items, 3d, etc. but am familiar with just about everything but I have ALWAYS had this problem. Just recently I have started to really concern myself with keeping my drawings "clean". I do not want dimension styles in my drawings that are not used and/or are not mine! Same with blocks! I would understand if I was copying block items into my new drawings that it might pull in some thing that are used inside the block that you may not see but this is happening when I pull in SINGLE LINES!!! ON LAYERS THAT ARE ALREADY IN MY DRAWING! It will pull in completely unused layers. I am at a complete loss. Sorry to be so aggresive but this is becoming a real nuisance. Any help is appreciated.

Can you post one of the drawings?