I think for those venues, the practical reason is that a battery of microphone stands would be visually intrusive, so they (esp classical venues) rely on mikes

I think for those venues, the practical reason is that a battery of microphone stands would be visually intrusive, so they (esp classical venues) rely on mikes suspended from the ceiling or clip on condensor mikes like DPA's. Additionally, violin and violists are notorious for swaying and turning away from microphones. In the studio, i think they generally start with large and small diaphgram condensors and ribbon mikes for good results.