Photos aren't only about quality, especially there days where it's popular to use lower resolution cameras, with worse optics. Specifically for portraits, it's common to use diffusion filters that reduce a bit details/contrast or do that in editing so you don't see every little "defect" on someone's skin.

Some people specifically want something other than their phones because they don't want to always have their phone or use it all the time, others want better controls or a different experience.