Why is that?
For a woman to preside at the Sacrifice changes the nature of what's happening on the altar, since she is standing in as Christ, the Bridegroom of the Church. Since she is willing to take that role, she clearly doesn't understand the meaning of what she's doing from a Catholic point of view. (Some Episcopalians take the Anglo-Catholic viewpoint, I always did, that's why I'm Catholic today. Others are more Protestant and don't believe in the Real Presence. I guess for them, it's no problem. But what we're talking about here is Catholic priests - who DO believe in the Real Presence.)
The other thing I noticed is that women don't function well as the head of a parish. Again, with the one exception (she now is rector of her own parish and last I heard was doing well) they couldn't do the administrative stuff either. You can talk and talk and talk (the usual female response to stuff) but eventually you have to make a decision and give some orders. These female priests either never made a decision and nothing got done, or they made a decision but couldn't delegate so wound up working themselves into exhaustion.
I think that only a certain type of woman tries to be an Episcopal priest - there are plenty of women in other fields that seem to be capable of decision making and delegation.