Countries often want independent capabilities even if it costs more.

And plenty of of launch types don't care about distance to the equator, for example polar orbits.

Lots of launch sites are very north, for example Baikonur, Plesetsk, and Vostochny.

UK is perfect for launches to about 55 degree retrograde inclination

You wouldn't want to launch into a sun-syncrhonous orbit from the Equator. Or from Florida or Cape Canaveral for that matter. The delta-V you start with which is great for an equatorial launch has to be shed to get into a polar or near-polar orbit.

From Scotland though, there's far less Delta V than Florida, or from French Guiana.

The UK's only orbital rocket launched from Australia. https://en.wikipedia.org/wiki/Black_Arrow

Some satellites have polar or higher inclination orbits.