I have never seen any "requirement" per se.
However, commercial reality dictates that a design have good L/D characteristics (or it will fall by the bean counters' wayside).
A reasonable present rule of thumb for heavies is that they glide (nil engines) somewheres around 2nm/1000ft .. which approximates 12:1.
As design and manufacturing technical capability improves .. so will the glide performance as a sideline consequence of improving L/D values.