Aikido assumes multiple attackers; throwing a guy just to let him back up makes no sense. The guy is still a threat, the threat needs to be taken care of.
That said if you do a technique with power on someone that doesn't know the ukemi a finishing strike shouldn't be needed.
Exactly: you would make the technique count, if you had to. In comparison with a throw, a punch to the face isn't much, and with other attackers...