That itch in the back of your mind telling you to learn?

I would guess that the system is also physical and without it you would die.
If you just sealed off the severed end, what I think of is a buildup like the body's way of healing blood vessels. Blood rushes to the damage and clots to prevent further damage. If the meridians can no longer flow, it would be like the clot getting to big, breaking off, and traveling to your heart and causing an infarction. In other words, it may cause a blockage in the system and prevent flow to the limb, which in turn would cause more problems. This is just a hypothesis though.
I think if you recreated the end of the meridian, it might cause more of a hole in the blood vessel that doesn't clot and would cause you to bleed out. Again, just another thought.