Performance mostly. But also even when made by various AAA studios, the resulting games often have this uncanny similar-ness to them. Personally i prefer in-house engines even if its just to maintain variety in the industry.
Also obligatory shout out to id tech for continuing to show off their engines with indiana jones.
ue4 was already bad in that regard. Really sad that cdpr dropped their own engine as licensed engines are wrecking the engine market (mostly epic tbh). Just so not worth it to delevop ones own.
like most engines, UE5 is whatever you hack it into being. I hate developing with Unreal but I do have to admit it's solid in a lot of ways. and has pretty mature content/LOD streaming, one of the biggest issues I saw with Cyberpunk at launch.