I personally feel a slightly bent bow arm allows for a better follow through than does a straight fully locked out bow arm.
In terms of physics, for every action there is an equal and opposite reaction that occurs at the same time. (And for every force there is an equal and opposite force).
When you release the string, I believe it is best if all forces are in line...and if this is done, when you release the drawing hand should go slightly back and the bow hand should go slightly forward. If the arm is fully locked, the arm can't go forward and the forward push (force/energy) you have in your bow arm will be find an outlet to dissipate...and since it can't go forward it may be more prone to cause a bow hand to drop, rise, or go to one side or the other. If that happens, a non-forward (out of alignment) energy will then be transferred into the riser of the bow.
This is my reasoning.
That said, if someone has been shooting well for a long time with a fully straight bowarm and does well with it, I HIGHLY RECOMMEND leaving them alone.
There is an old saying, "If it ain't broke, don't fix it."
Trying to change something that works is a great way to destroy success.