We have assessed the relation between electrohelicity and optical activity by analyzing the MO contributions to the electric and magnetic transition dipole moments. In allene and longer cumulenes there is a fundamental connection between their chiroptical response and helical frontier MOs, which we use for rational design of optically active molecules. However, we also show that the link is not universal, as we find no direct relation between orbital helicity and optical activity in polyynes and spiroconjugated molecules. There is thus a notable variation in the origin of enhanced rotatory strengths in molecules with electrohelicity. These results question if electrohelicity is at all useful as a general concept for understanding and developing novel optically active molecules. When helical π-systems are suggested as an underlying mechanism for a large chiroptical response, it must be supported by careful analysis on a case-by-case basis. Indeed, we found that in allenic systems, such a mechanism involving helical MOs can be used to enable enhancement of optical acitivty using substituents and macrostructures. This insight is to be applied for design of molecules with large chiroptical response.