There was even a time, albeit brief, when press releases had their hay-day online. For 250 bucks you could get your news story published online on all the major search engine news rolls. During that time (6 years ago maybe?) you would actually get a link from your news releases, and those links were found on news sites (pretty important websites). That meant increased ranking for your website.
So hack SEOs clamoured to release pressers, of course, 95% didn't have 250 bucks to spend on a legit release, and fewer still wrote a presser for--well--the press.
These hack SEOs today tout press releases as a viable tactic to get relevant incoming web links. Incoming web links are a key factory to help you rank, but these links never come from press releases.
PR are supposed to be for the press, and now the press says they rarely pay attention to them, ergo, stop using press releases. Furthermore, if you encounter anybody claiming press releases as a viable tactic in SEO steer clear away. The individual or company is fraudulent/manipulative/ancient or worse--ineffective.