I think digital watches became less popular in the late 1980s when analogue started to come back into fashion. Probably driven by the fact that you could get fashionable, decent quality quartz analogue watches like the Swatch for not much more money. It was watches like these that kept the Swiss watch industry in business. Digital made a comeback in the late 1990s/early 2000s with watches like the Casio G-Shock but it seems to be mainly analogue again now. I suppose digital watches will always be available as they make sense for a lot of people and are good for children but they are not 'cool' like they were in the late 1970s/early 1980s.