Why do dialect boundaries in Scandinavia not always match national borders?

Dialect boundaries in Scandinavia do not always align with national borders because linguistic transitions between regions are gradual rather than abrupt. These boundaries reflect historical patterns of settlement and communication that predate the establishment of modern political frontiers.1234

Because these linguistic shifts occur as a continuum, traditional divisions into specific dialect areas are considered somewhat arbitrary. While national standard languages have been promoted through education and high literacy rates, rural communities have maintained diverse local dialects that often share more in common with neighboring regions across a border than with the urban centers of their own nations. Consequently, the development of these dialects is rooted in local geography and historical social ties rather than the administrative lines of modern states.13