Controlled Vocabularies - why should I care?

Look at the following journal article titles and their associated MeSH terms that I've selected from MEDLINE.

Notice the authors have used different ways to describe kidney calculi -- kidney stone, kidney stones, renal stone, renal stones. The appropriate MeSH term is Kidney Calculi which in each case is part of the list of terms in the MeSH field.

Why should I care? If you use the MeSH term Kidney Calculi, you don't need to search all the synonyms!

TI: Calcium may cut kidney stone risk in younger women
MeSH: Calcium, Dietary/administration & dosage; Kidney Calculi/ prevention & control; Phytic Acid/ administration & dosage

TI: A 44-year-old woman with kidney stones.
MeSH: Insurance, Health; Kidney Calculi/diagnosis, epidemiology, physiopathology, therapy; Kidney Calculi; Obesity; Risk Factors

TI: Urine examination for calculogenic crystals in renal stone patients--a newer approach using refrigeration
MeSH: Calcium Oxalate/urine; Case-Control Studies; Kidney Calculi/urine; Predictive Value of Tests; Urine/chemistry

TI: Crystals, Randall's plaques and renal stones: do bone and atherosclerosis teach us something?
MeSH: Arteriosclerosis/ physiopathology; Bone and Bones/metabolism; Calcium Oxalate/metabolism; Crystallization; Kidney Calculi/etiology

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For this example, only selected MeSH terms are displayed from the MeSH field for each article.