Why is it contraindicated to aspirate syringe and stroke site during heparin injection?

Why is it contraindicated to aspirate syringe and stroke site during heparin injection?
Heparin , an anticoagulant is to be injected into the fatty layers via subcutaneous( sq). A short syringe a Tuberculin syringe can be used. Do not aspirate and do not massage site . Heparin interferes next to the conversion of prothrombin into thrombin; prevents the conversion of fibrinogen into fibrin = inhibits clots. Aspirating and massaging defeat the purpose. It causes injury to the tissues and causes spare bruising. Clots or hematomas can be formed by the action.
You don't polish it as it can cause increased bleeding below the skin and bruising. Best thing is to inject into subcutaneous skin and give up your job it alone. There's no need to aspirate unlike insulin - it's ok for heparin to enter the blood stream.