How often are you in the scenario that you you're on a phone call and need to tell someone where something is in a document versus communicating with them online where you can send a link though? Every work meeting I've been in for the past nearly a decade now has been through something like Teams, Slack, Zoom, etc. where I can send text.
Also PDF viewers are the baggage in the scenario. Everyone uses web browsers everyday. PDF viewers are the odd one out in the majority of people's "tool chains".