Wards lose health over time.

As the wards start to lose light why are they still as strong from when it was just placed. When a candle starts to burn out it melts, goes away. But wards just stand there. What if when the timer reached the edge of one of the three health packs they lose that bit of HP so that when the ward gets spotted by a trinket it saves the extra 2 seconds. kthnxbai (I am really tired please be gentle)