Definately. I agree with all of the above, and for a simple tactical reason, you may not choose how an attacker moves in on you, their speed, which side they move in on, also local geographical positions may dictate how you may be able to respond. Beside a wall, in a croded bar, with your girlfreind/ spouse/ etc holding omto your hand.....
Or injuries to your preferred side....
(this list could go on and on....)
the other part of it was, I did do some training at another dojo (non aikido) where almost all attacks were right handed. coming in with a left hand yokumen uchi really caught them unexpectedly.
And as we know, not everybody will move to strike in an expected pattern.
so best we train to deal with it.