In this version, Holmes is an out of towner with no reputation. At this point, any other cases, murder or no, must come via some character's personal life.
The nearly exclusive fixation on murder has been a weakness of all mystery fiction other than the caper/heist story for decades. Criticizing Elementary alone for this while giving a free ride to every other cop and detective show is quite strange. Nor is it any more a hoary cliche than a male Watson. It is just something that was regarded as essential but turns out not to be after all.
CBS aimed that hoary cliche Joan Watson straight at the enervated faculties of the vile old folks, dontcha know?