The real answer is CW isn't that profitable as other major Networks like FOX NBC and ABC.
CW's business model use to be let certain shows run despite the ratings than syndicate those shows like Smallville and Gilmore Girls and recoup money on the reruns.
The CW started doing a little better once they found their second niche. It use to be just a network targeting teenage girls then they also started targeting superhero and Syfy fans. This is probably largely thanks to Supernatural (don't quote me on that). It also became a network that would pick up other shows that other major networks wouldn't take like Supergirl (CBS) and Black Lightning (Fox).
I don't know if there will be many buyers for the CW. It doesn't make sense for Disney. Amazon might have an interest at the right price, but it would need to be a big company at the right price that could leverage CW's content libraries. It doesn't make sense for Netflix (the companies still in the red from spending too much)