Some women's tennis matches are extremely boring. If you watch Serena or another top female vs. an unranked player or someone in the first/second round of a tournament, the sets are usually 6-0, 6-1, with hardly any good shots or long rallies. At least in men's tennis, even if you see Federer or Djokovic play in a first round match against an unranked player, you still get some good points, longer rallies and fantastic shots. You can get some great women's matches later on in the tournament, but even some of them could be very lopsided and not entertaining.
Serena Williams and Venus Williams in 1998 claimed they could beat any male tennis player outside of the top 200. Karsten Braasch, a German tennis player, ranked 203rd at the time, who was the end of his career, and smoked cigarettes and drank beer when practicing, beat Serena 6-1 and Venus 6-2.