Cre-Lox systems predate CRISPR/Cas9 or CRISPR/Cfp1 approaches by quite some time. If one exists for the system you want to study, they also tend to work better. (floxing the original mouse is, however, substantially harder)

I don't think it's entirely accurate to say that conditional editing of DNA is a new thing. The ready accessibility and combinatorial possibilities, yes, but for targeted conditional knockouts, floxing mice has been a thing for about 20 years now.