Skis have a sweet spot - this is the best place for the skier to apply pressure to get a great response from the ski. It usually is determined by the construction of the ski: the shape, the flex pattern but also the bindings mounting point, see Factors that determine the ski behaviour.
The sweet spot is somewhere in the middle, but this doesn't mean we should stay on top of it all the time - just when we need to use it.
In fact, to be able to apply pressure on the sweet spot, the edge must be firmly engaged and that edge engagement starts with the tip of the skis. If the tip of the ski does not engage, then, by the time we need to apply pressure, we have less edge to work with, the edge will engage later and not as strongly, negatively impacting ski response and performance.
It is good, when evaluating new skis or switching skis in the middle of the day, to find the "sweet spot". This is especially critical if you're looking to start carving some stiffer or longer skis (GS etc).
It is a good idea to spend a few turns or runs on a green slope, where you focus on carving the new skis: put them on edge, stand on the outside ski and move fore/aft from the ankles until you find the sweetspot - the spot where the carving ski reacts and turns nicely. From there, move to a bit faster blue run and explore that spot at higher and higher angles.