Obvious reasons escape me
Ma-ai is the appropriate distance between me and my partner. if we are dancing ma-ai can be very close indeed. However, if we are practicing a given technique in the dojo, then the ma-ai needs to be appropriate for the technique being practiced. Thus the ma-ai for a grab is of necessity closer than that for a Yokomenuchi, Munetsuki or Shomenuchi.
Atemi, as a substitute for moving with Aiki and following the principle of Shodo-o-Seisu (Control the first move), does not necessarily mean your technique is going to work. The time spent effecting the atemi is time which could be put to moving in a safer position.
As to someone charging full tilt at you, try this experiment run as fast as you can and throw a punch or strike in the direction you are travelling while you are moving. If you do not fall down first, you will discover it is next to impossible to do so without slowing up or executing your strike at the last moment as you stop. Aikidoka would do well watching a broken field run for a touchdown in football by a receiver for how to deal with such charges.
I suppose we can continue discussing the value of atemi.
My point remains. Atemi take time. Only occasionally are they even "needed".
Aikido still must engender the practice of "Aiki".