You are comparing apple to orange. Not only Graf, but Court, Martina, or Chris had all the ridiculous tennis records that where no single legendary players from ATP ever came close. On average, it's easier to win in the WTA and setting records. Life in the WTA is easier b/c in men's tennis it's more physically demanding, playing 5 setters instead of 3. Their limitation is due to more stressful, more wear and tear.
Chris Evert made 33 GS final. How many male player ever came that close? Even a longevity player like Connors, or very fit Lendl, Federer numbers look silly.