I often carry a buggy up several flights of stairs, sometimes also carrying the occupant in the other arm, and I have never managed to hurt myself.
I often cross the busy road outside my house and have thus far managed not to get knocked over - it doesn't mean it won't happen does it?
Incidentally, whilst the baggage handlers are pi*!*g about running up flights of steps with buggys what about everybody else's luggage? Let's not forget that many airlines, particularly in the low-cost sector, operate with small baggage crews. But, hey, as long as your buggy is waiting for you the second you step off the aircraft then to hell with everyone else's luggage, they can just wait that bit longer...the tail wagging the dog methinks!