For two reasons, atemi should be considered:
1 ) Atemi are often part of how to ensure the success of a technique.
2) If uke is confident that tori will make no strikes or kicks, uke's behavior is not "realistic" at all.
Amen to that! The attacker in the Shodokan knife competition clips, for instance, would be approaching the defender rather differently if he knew he could be struck in the groin or face. I've seen this effect in randori often. When the attacker knows a technique may be accompanied by a blow or two, he/she doesn't approach nage with the same confidence and recklessness that you see typically in randori where strikes by the defender are prohibited.