Monica wasn't that bad looking when she was younger.
I think what Bill found attractive was her willingness and the power he could have over her. She was willing to stay quietly in the background until Bill wanted a blow job, come in and service him, and then leave.
There seems to be something similar going on with the current mistress -- she comes over when wanted, and leaves when it's time for her to leave.
For some, the whole point of seeking power is to be able to have women who will subject themselves to your will.
Monica wasn’t that bad looking when she was younger.
Her mouth still looks good to me.