BF 109 canopy and bailing out

[III/JG53_Don]

I guees the reason is that if you ditch it can be likely that your canopy can be pressed back into position if it is still on the right side of your plane. Imagine the plane ditches with a grade to the left and the gravity forces the canopy back into position.... not amusing when your plane starts to flood

If its jettisoned you can escape from the plane from both directions