I get what you're saying. However...
Hitting is more about whole body strength and technique than it is purely upper body strength. Also placement of the punch. And yes, men simply have more muscle mass even talking about whole body - assuming all things equal - than women do. However, that would mean a woman's kicks would be weaker than a man's kicks...and going with that idea, a man's kicks would be more powerful than a man's punches...so why aren't the men also kicking all the time to get more impact? They do, occasionally, in comics, but it's more like 'women, occasionally, use hand strikes in comics' than anything.
And kicking isn't always the greatest idea. I can roll my way through three, four handstrikes - good, solid ones, not just flicky-flicky crap - in the time it takes me to kick and move into the next kick. Additionally, kicking will - obviously - for a moment put me on one leg. That's not a place one wants to often be in the middle of a fight. Even as a smaller guy fighting a big man in full-contact sparring, I learned pretty quickly that trying to rely on kicking (due to reach) was a losing game.
There's a time and a place for kicks, and yeah, they CAN be more powerful than hand strikes, but.
And then, as you say, we're talking about women who in-comic hit as hard as men do. Shiva, in her first fight against Batman, was noted as hitting as hard as the Sensei, or R'as, can't remember which. Orphan-Cass - in the same comic the artist shows her doing kick, kick, kick, panel after panel, casually snaps a very thick steel chain with a hand-strike. Etc.
So, agreement, the kick to compensate isn't logical. It's not even tactically sound.
And yet I still see it, over and over again.
Bring back Damon Scott. ^_^