1. Russia does not have an infinite supply of stand-off missiles. They're already having to use older, less precise, models and adapt missiles designed for other purposes to the purpose of bombardment. Eventually Russia will run low on those, too. From a strategic POV, when supply is limited, usage should be focused on points of greatest need. The Russians have not done that and are wasting their limited quantity of their best munitions. As the Germans demonstrated with their London Blitz, dropping explosives in random civilian areas is not likely to succeed.
2. The curious thing about the Russians' offensive against Bakhmut - begun in August last year - is that it was of little strategic value for the Russians. They spent huge numbers of men and material for little strategic purpose. OTOH, a Ukraine breakout from the Bakhmut area would put several major cities in "danger" of being liberated.