Ignoring hard failures (like a battery case overheat+rupture)...

Running out of fuel is, unfortunately, not as uncommon as it should be. Most aircraft glide quite well (10:1 glide ratio). I really cannot tell with this plane, but the lack of control surfaces make it a meteor.

Because we have decades of experience with the existing engine & fuel types, but very little experience of battery powered aircraft?

Not with battery powered aircraft, but quite a lot with battery powered anything.