Why is the quality of the interactive render area so poor?

Question

3D

Answer 1

Because by default it is made in order to quickly evaluate the settings of the scene in terms of color, light or textures. And for this, the designer needs a fast render. Therefore, the quality is bad initially bad.
But if you want better quality, then there is a barely noticeable slider on the right for this. Yes, you probably didn't notice it :)
Pull it all the way up and the quality will be 100%.