From a historian’s perspective the reasons are simple:
- In the past, as the minority of Protestants in a largely Catholic Europe, Scotland preferred to be part of a group rather than stand alone. With religiosity on the decline, that identity isn’t as strong any more.
- During the time of the Empire, Scotland reaped lots of economic benefits of being part of the union. These days economic benefits of the union aren’t as strong.
- In the past, geography mattered because as an island nation, Scotland could better defend itself. Now that matters little.
- Britain is held together by the English, who are London-centric and don’t give the North as much attention as it deserves.
- With the EU, both Ireland and Scotland have a new centre to identify with other than London.