If the first stage is a SpaceX-style reusable stage, is there any benefit to a jet engine? I suppose perhaps it is more reusable, AFAIR the SoaceX stages have s

If the first stage is a SpaceX-style reusable stage, is there any benefit to a jet engine? I suppose perhaps it is more reusable, AFAIR the SoaceX stages have short-ish lifespans.