Also it makes life much easier for the designer to change what engine is fitted, since by and large only the pod needs a redesign, not large chunks of primary aircraft structure. Can you imagine the task of installing a bigger engine in a DH Comet.
And it saves a complete re-think on CG positioning if a sunstantially heavier (or lighter) engine is fitted later, podded engines are pretty close to the CG operating range, tailmounted engines are not.
G