This is something that began long before AI art. Look at the popularity of Thomas Kinkade - The Master of Light! Many AI generated images, when not refined down, now have that same sort of aesthetic. I have found that Googles Nano Banana generation is particularly susceptible to generating that cozy glow kind of style than many gravitate to.

It is art stripped of the humanities. Pleasant, non threatening, technically very capable and totally disposable. The Big Mac of creativity.