That's true. The rate that we've seen them split in our tank has been about once a year.
It's the same thing when people make fragments of their SPS colonies, only worse from the point of view that damage may occur. When you frag an SPS colony some of the individual animals, part of the colony, are killed where breaks are made. So, one could argue that we shouldn't do that, it kills animals. However, taking them from a reef is certainly worse, a higher opportunity for loss, plus the removal from a reef and the collateral damage that occurs there too.
We believe it's best to culture these animals in tanks. SPS, LPS, mushrooms, anemones, etc. The demand is certainly there so if it isn't filled by people who culture, it will be filled from the ocean. A worse choice from my point of view.