if you measure the current in any two points equidistant from the feedpoint and find unequal currents then you have a problem whether you're aware of it or not. if you're feeding a dipole (balanced) with coaxial feedline (unbalanced) then current is not evenly distributed along both halves and common mode current appears on the outer shield of the unbalanced feedline, period.
common mode current destroys pattern symmetry and reduces the amount of current generated in the e-field, reducing efficiency. you don't know about those problems if you are unable to measure the field strength of the pattern and/or unable to measure rf current in the elements as described above.
only when the two halves of a dipole are at perfectly opposing electrical potentials is maximum current produced. since that's not possible when feeding a balanced antenna design with an unbalanced feedline, common mode current exists on the outer shield of the unbalanced feedline, sans the required matching device/s.
properly constructed 1:1 current BalUns and rf chokes both have the ability to superimpose a high imepdance upon the outer shield of unbalanced feedline to suppress common mode current, forcing the current back into the dipole and balancing the opposing potentials of both halves of the same, restoring pattern symmetry and maximizing current in the e-field.
