Because as they said at the time, it is "considered outdated, inefficient, and too heavily reliant on strength of schedule, often disadvantaging mid-major teams". In the softball context, mid major is anyone with conference limitations (like VT this year) and can't get to Clearwater or other early season showcases where top teams play each other. The fact that Stanford got very little RPI boost from sweeping FSU is silly. Not sure how the NCAA can justify saying a ratings system is outdated for one of their sports but is still the gold-standard for another. Not surprising, of course, since it is the NCAA.