For me the reason is completely different. I really want to switch to unreal engine 5 but I want to make grand strategy games and unity has a toolkit on the asset store that handles the map, pathfinding, units and a lot of other features.
I love strategy games and I saw an interview with one of the EU5 developers who said that managing a lot of units was complicated in EU5. It is possible to do it, but in C++ and not in blueprint.
So very few strategy games are using UE.
At the beginning EU was really specialized for FPS, it has improved a lot but there are still some details that are sometimes painful when you do something else like strategy.