they were a traditional glass image for cask drinkers in the 70s/80s, whilst the straight glasses were for the modern Euro style lager drinkers which grew massively in the 80s, so there were kind of lots of things going around then that led to their sort of demise not just they were considered old fashioned, but theyre really easy to chip, whilst the straight glasses which are all nonic, arent, they also take up way more space on bar shelves, and are a pain to fit in the dishwasher, and they were way more expensive to produce, all of which meant most pubs quickly switched, plus breweries used to love putting logos on the straight glasses, harder to do on dimpled mugs, and would send out so many boxes most pubs would be overwhelmed, these days of course they charge the pubs for them.
so yes dimpled mugs have made a kind of comeback of late, but theyre still quite niche imo, often in craft bars where its almost gone full circle retro nostalgia on them.