Maybe most people do not think that they are bad at dating. They think that their pictures look great. They think that their profiles are good. Therefore they are not looking to optimise further. Not getting any dates is explained away by the faults in others.
Also nefore reading this post I had absolutely no idea that things like this exist so it would not have crossed my mind to look for something like this if I had to create a dating profile.
Someone might also think (either consciously or subconsciously) along the line of - this site is giving me feedback about me. I have a prior estimate on how datable/likable/pretty I am. Getting a lot of direct feedback on these aspects might make me re-evaluate my current position about me and that is scary. For some scary enough not to do it.