I think current dropwire terminal boxes employing jelly locks to make the connection to internal house wiring are more about appearance than anything else. As already stated here, a properly made jelly lock will exclude water very effectively but looks much nicer in an enclosure. Ours is a small black box about 3 by 2 inches and looks the business. I have seen flooded footpath chambers with jelly joints in, and circuits were unaffected. At the pole end, the old grey dropwire number 2 was intended to be terminated under screws without stripping the cable ends using " insulation displacement " technology, but most engineers didn't trust them so stripped back anyway
