also, kotegaeshi has a certain set of pre-requisite move in order to take uke's balance. So, it's easier for us to twist their wrist.
and moreover, most of aikido techniques requires a flowing force from the opponent. If he's standing still, It will be hard.
Various basic kotegaesi demonstrated by Nemoto sensei. Some of them start with no initial energy, e.g. katatedori and a few ushiro techniques