I think the answer stems from our cultural tradition of patriarchal Christian religion. In Christianity, "God" is not only a title, it is a name. While we know "El" is the Hebrew name for "God," in English we just stick with "God." For a nerdy example- it's like how "Doctor Who" goes by Doctor and it is both a title and name. He's just "Doctor."
"Goddess" on the other hand, has been much more limited. In Protestant-idea-entrenched America, the word "Goddess" is only used in referencing non-Christian pantheons. "Goddess" was a word for what other people worshiped. Indeed, she is the Other, and not like my God- and not like me. Except that when it comes down it it, I'm not like my God either, I'm more like the Other- and indeed I am the Other and that is where Christianity starts separating itself from women. What is unique to Mormonism is that we do believe in a Heavenly Mother- so we have the potential to no longer treat women as the Other and include them as equals- equally potential to reach the status of God and Goddess. Unfortunately, as Mormons, we haven't made that step to really include Heavenly Mother into our reverence. And that's why I started this blog: to include the Mother in our thoughts- and to include women into what it means to be godly (goddessly?).
I had been thinking about this idea and then while I was reading Dance of the Dissident Daughter, I found that Sue Monk Kidd said it well,
An uneasy reaction to the word Goddess is common among women. Thousands of years of repression, hostility, and conditioning against a Divine Mother have made a deep impression on us. We've been conditioned to shrink back from the Sacred Feminine, to fear it, to think of it as sinful, even to revile it. And it would take a while for me to deprogram that reaction, to unpack the word and realize that in the end, Goddess is just a word. It simply means the divin in female form.So as I continue this blog and continue to put "Goddess" in my scripture study, I also hope to "unpack" the word and let go of the connotations of "Other" and accept the person it represents, not only as someone as awe-inspiring as God, but as my own potential. And my daughter's. And my son's. And yours.