It's all about the chemistry.
The problem with vinegar is that the concentration of acetic acid in vinegar is very low, about 4%, if I recall
correctly. With that level of acidity (ph is a different issue) it takes a long time and a lot of vinegar to clean out a large build up.
Small amounts of scale might be cleaned with vinegar and as a preventative measure may help and does no harm.
Muriatic acid (HydroChloric Acid) sold in hardware
stores is about 30% acid and is pretty strong. Out of the bottle it will blast through scale in minutes. Diluting it to 15% might be prudent. If I remember the chemistry correctly, it breaks down into to calcium chloride (a salt) and carbon dioxide and some other salts.
Phosphoric acid will also work. Sew Clean is product sold to clean black water plumbing
. The problem with phosphoric acid is that it breaks down into phosphates which is fertilizer and a chemical the US has been trying to get out of the water
because it promotes algae growth.
"Agricultural" or "horticultural" vinegar is 30% acetic acid which should work better than plain old white vinegar.