People today have no idea what it was like in the old days. Coal soot is NASTY and it made its way everywhere. A crack in a flue and oh my!!
So were your house's walls furred out? Or have wall cavities been used for return vents? Were plumbing stacks added thru the attic? Wire runs?
With new incentives you might want to consider new attic insulation - use the foam hands down.