Why is using molasses helpful?
The ‘theory’ is that molasses (sulfur-free) is beneficial to the soil biome and helps it to break down salts, making them more available to the plant. Not worth the time in media other than soil and not recommended at all for hydro.
I never found it to make any difference one way or another. Paying attention to proper lighting, nutrient load, environment etc will have the greatest impact IMO.
Read the Growers Bible, tells about Molasses.