I forgot to say why. Ivory has natural coloration and variations that I find very unique. As a fan of natural materials, the only runner up is ebony as far as untouched/unenhanced beauty. While ebony does have its own satin feel ivory takes it to another level. Lots of people say ivory is fragile, and I believe it can be. I wouldn't want to drop my knife on concrete that's for sure. With that said, I have a couple 1911's with both bark elephant ivory and mammoth ivory grips. Thousands of rounds and no problems yet. Anyhow, my ivory knife is a very special knife. I don't carry, use or handle it in the same fashion as my EDC carry knives. The real tipping point for me is how Ivory looks good in any light. Bone and stag can look a little odd in certain lights. Ivory, and ebony actually, always look good to me.
It may not be my favorite material for an EDC, but I hold Ivory very highly in my views. I'm not even a hunter either. So go figure.
Kevin