I agree. I think he hasn't experimented with different hairstyles because he wants their appearances to be idiosyncratic. I like Sarah's puffy ponytail and patented heart-shaped hoop earrings. I like Lana's bronze tone, her ponytail and the two large strands of hair that frame her face. I like Amanda's sleek brown mane, and her beauty mark. It gives them each character. But it wouldn't hurt to shake it up a bit when, for example, they're having sex in the shower. I would love to see that (Sarah for the first time, and Lana and Amanda again.)
I have Lana and Sarah ranked one and two, respectively. In reality, it's more like 1A and 1B. And while for me, Lana, is undisputedly more attractive, even with the both of them sporting the handbra and blue jeans, I think the main female characters in these three discussed comics can justifiably be atop anyone's list whether it's Lana, Sarah, Amanda or Alexa.