A 50mm prime is often chosen on APS-C because it fills a different role than the kit zoom. Its field of view is roughly equivalent to 80mm on full frame, which is a classic portrait focal length: flattering for tighter compositions and better for isolating subjects with blur.

The 50mm also has a slight speed advantage at f/1.8 versus f/2, even if that difference is small in practice. In addition, 50mm designs are typically simpler than 35mm retrofocus designs, which can make them easier to produce well; they are often regarded as slightly sharper.

A wider field of view is not automatically “better.” Many photographers want their second lens to complement the kit lens rather than overlap it. Since the kit zoom already handles the wider end, a longer prime gives something meaningfully different for portraits and tighter framing.

So the preference usually comes down to use case: 35mm is often better as a general walk-around focal length, while 50mm is popular when the goal is portraits, subject separation, and a stronger complement to the standard kit zoom.