Molasses is not used directly by the plant. It is broken down in the soil by microbes into primarily nitrogen, potash and various micronutrients. The carbon is also a good source of energy for the microbes in the soil which allows them to multiply more frequently. More beneficial microbes in the soil means a healthier soil.
Chemical fertilizers already have the three primary minerals in a greater abundance than that provided by molasses, and MG also provides all of the essential micronutrients.
So what does this mean? Well, if you are using no chemical fertilizer and are attempting to grow completely organically then adding molasses may be of some help. If you are already using a complete chemical fertilizer, such as Miracle Grow Bloom, then I do not see what benefit you will get from adding molasses, as the chemical fertilizer already has everything the molasses has and in much greater amounts.
But if you want to add molasses it shouldn't hurt anything.