Probably because that's better left to the RCPS3 site forum itself where you'll find people who actually consistently use RCPS3. As you might've noticed, there are very few RCPS3 topics at all here.
Cemu was originally released on GBAtemp, which explains why way more people are interested in that vs RCPS3, and compatibility wise it's already miles ahead of RCPS3 so more people are interested in that.
Not to say RCPS3 isn't an awesome emulator, the fact that a PS3 emulator currently exists with playable commercial titles in and of itself is extremely impressive. Its just not overly popular here.