It’s a balancing act.
There are a bunch of topics of people trying to host their forums for as cheap as possible and complaining that images are taking too much space. This type of admin doesn’t care about quality of the images, all they want is to cut every corner and reduce costs.
On the other side of the spectrum you have people who are really invested on their communities and will leverage object storage and be able to provide a good quality with reasonable costs.
The discussion here is about defaults right? Or maybe we could try to measure the jpg size against the png post optimization? If I remember correctly the png optimization can be quite expensive…