I would say that if the people/business which are affected by this, should have registered the plural for protection. Maybe they think it is not important, as long as they have the trademark to protect them. Who knows? Without asking them. It might be more important if they don't have a trademark. I generally try to buy both, if it makes sense. I've even paid good money to add the plural to my singular. Sometimes I've even been sloppy and not registered the plural, and the registrant has put a business website up on the plural. Meaning. It's not for sale anymore. (Although everybody has a price... but anyway, out of my price range.).
I don't see much of a dangerous trend. It's been that way for some years already.