Why is lemon juice made with artificial flavor, and dishwashing liquid made with real lemons?
Lemon juice is an acid and relatively weak. Drinking lemon juice in its diluted form (half a lemon to many ounces of purified water) can help conditions like heartburn, diarrhea, and constipation due to indigestion. It also prevents pathogenic bacteria from being present in the digestive tract. Can you imagine what will happen if you drink a 12 ounce cup of pure lemon juice? You harm your stomach because citric acid will puncture the inner linings of stomach causing peptic ulcer (very painful).
When and if that happens much of HCL will be released and now you have a powerful acid (HCL) and a weak one interacting together causing even more damage.
As to the Dishwashing liquid I think lemon juice interacts with the surfactant agents of the cleaning liquid (mostly hydrocarbons) to release the surface tension of oil and fat molecules present in the dishes. Hot water is needed to make the breakdown of those molecules even easier. Lemon juice also give a nice aroma to the newly washed dishes.