The John Muir Way project is complete - though no doubt there are signs to be added or revised.
Long distance 'themed' walking/cycling routes are not new - and more are coming. The reasons behind them will be a mixture of encouraging people to discover 'the great outdoors', devising a nice/sensible/challenging route that can be followed in sections or 'end to end' - helped by good signage - just for fun or as part of a serious tourism plan.
The JMW is slightly unusual as it has recommended/signed alternatives for cycling in some places. Some people will only follow the 'cycle route' others will follow the 'walking' routes - especially if they look more interesting.
Last week I tried some sections in East Lothian. The first (walking) bit going east from Dunbar included a bit too much sand and too many steps for my liking, but the 'walking' route from Bellhaven to East Linton, along the coast and up the Tyne was delightful.
The signing is much better than a lot of Sustrans routes though the path is very narrow in places and if it had been created by Sustrans as a cycle route would come in for a lot of criticism!
Fortunately in Scotland such paths are available to bikes for 'responsible use'. There have always been people willing to use paths on bikes - especially since mountain bikes became popular, but there must be plenty of scope for new routes that are perfectly cyclable without being particularly wide or tarmac/whin surfaced.
I was particularly impressed with a path along a field margin - presumably a longstanding Right of Way. Presumably there is also some agreement where the farmer doesn't just 'forget' about it and plough right to the edge of the field.
This is one of the few signs that is 'easy to miss' -