It causes problems for pop singers* because many pop songs use a rhyme between "romance" and "dance" that works in Am English but not in Br. English. Most singers use /Š/, and some insist on using the two distinct phonemes.
*PS Not all pop singers - just (or chiefly) the ones whose accent is like RP in the case of these vowels. But when The Beatles sang Devil In Her Heart - for example - they didn't have to force the rhyme between "chance" (/ɑ:/) and "romance" (/Š/), because the words do rhyme in their dialect.