I'm (CS-grad) working as an intern with people working on the LHC and KM3NeT, ROOT/cint is used extensively there. It's unbelievable the blind love these scientists have with c++. The reasons so far I heard are: "it's fast" referring to C++ and ROOT.
Furthermore cling - also used in the ROOT project - perhaps is a more modern approach in the C++ interpreter scene. It's based upon LLVM and can do JIT (and probably better c++11 support)