In general, the best image quality comes at the lowest ISO setting for the sensor. I suppose you could call that the maximized setting and never change it....
However, many photos can't be made at ISO 100, which is why we have the ISO dial. There is a reduction in absolute image quality, of course, but that is often acceptable when it means getting the image in the first place.
All images "could" be shot at ISO100 but it might not give satisfactory images or be the best choice in some cases.
Given a shot that tends to be under-exposed, and that other options are at their limit or fixed (exposure time/IS, aperture, flash,...). For most cameras, the image may be "less noisy" and perhaps "look better" if you increase in-camera ISO rather than just fixing the exposure in e.g. Lightroom, although there is a greater risk for blowing highlights. For certain cameras, the same can be achieved by using the sliders in Lightroom with the added benefit of not clipping the highlights in the raw file.