I think that all serious offshore
racing crews use some sort of shore based team to guide them in mid- and long term decisions. The on the spot and short-term decisions are made onboard but with a big influence from the shore support too.
The other group of people who use weather services are bigger
boats with less experienced owners on more demanding passages.
The third group are owners and crews of boats of all sorts and sizes with some sort of shore connection (often via a sat phone) but little or nill understanding of the weather. This will include sailors and rowers, backpackers, mountaineers, etc..
I have not yet met an experienced cruiser with good weather skills to use a router. Such people tend to invest in
equipment instead. However, I believe that for the more demanding areas (I would guess the arctic waters, the Southern Ocean, etc.) even such experienced sailors will seek some form of shore weather support.
b.