Well PageRank is still around but Google just does not share what the PR numbers for any given website are. They keep that information to themselves now so that people have a harder time of tampering with their rankings. I really didn't understand why they made it public in the first place years ago.
Now as for why people are clinging to PageRank, I really couldn't begin to understand other than the fact that they just don't want to move on and find other reliable information that they can use to help to determine the value of a site as far as SEO and rankings go.
I have actually seen people that are still listing backlinks, guest posts, domains for sale, websites for sale and they are stating PR as one of the metrics and stats for what they are trying to sell. Any PR info that they would have is probably way off of what the real PR would be for the site or domain in question since even the older PR sites that tell you the PR are using data that is years old and not accurate.
I doubt that Google will ever reinstate the public's ability to know the PR of a site so they need to just move on from thinking or worrying about PR and just use some of the other metrics that can be found like DA as you stated.