Medium format systems are usually built for maximum detail, tonal quality, and controlled-light work rather than extreme low-light shooting. Historically, larger formats have been used to capture more detail, and in digital that still tends to mean pairing the larger sensor with high resolution.

A lower-resolution medium format sensor could use larger pixels, but that does not automatically make it a compelling product. The main audience for medium format typically wants the extra detail and image quality for studio, landscape, fashion, and commercial work, where lighting is controlled and low ISO is preferred.

In practice, high-ISO shooting also reduces usable detail because noise rises as the signal is amplified, which works against the main reason to choose medium format in the first place. So manufacturers generally optimize these cameras for low-ISO image quality instead of high-ISO performance.

Also, medium format lenses are typically designed for image quality and coverage rather than low-light speed, so the overall system is not usually aimed at nightclub, event, or paparazzi-style shooting where high ISO is most critical.