If sometime it feels like central banks have "have your back" when trading stocks every single day since the collapse of Lehman, you are wrong. They only have your back every third day, because according to Bank of America there have been a ridiculous 572 rate cuts around the globe since the fall of Lehman, one every three trading days!
Perhaps this explains why with 572 rate cuts in the rear view mirror, which have succeeded in pushing global stock markets to record highs and yet have failed to either unleash the "wealth effect" for the rest of us, to stimulate inflation, or send US GDP into a stable, 3%+ growth trend, in fact culminating with the most recent GDP contraction during the so-called recovery (at least until all negative data is revised positively), one can see why the Fed is just a little worried about breaking a trend that has been working... if only to create the illusion of paper wealth for a select few.
P.S. the number above of course does not account for the $13 trillion in direct liquidity injections central banks have conducted since 2008, which have flowed through directly into both the bond and the stock market, leading to unprecedented bubble in both asset classes.