A feat that is stated that is worse than another feat the classes get with a feat tax of two additional feats would cause most people to get the better performing feat.
Planar Conduit and Mummy's dust both cost one feat. I cannot speak for anyone else, but I have enough spreadsheets at my job. My fun time I play simple. If it is simpler and more fun to play a cast which summons, and I can help my friends I'll do it. The more restrictive this feat (which exists to stop a gap in a class and provides an alternatives) is by requiring several feats to work the less likely it will be used.