Why does Robert Browning so often choose painters as the speakers for his monologues? Why not choose poets?

In poems such as "Andrea del Sarto," Browning wants to explore the dilemma shared by many artists: should one try to achieve high art or remain content with commercial success? The subject of this particular poem reluctantly opts for the latter, largely to satisfy the demands of his worldly and materialistic wife, Lucrezia.
Browning uses artists, as opposed to poets, to explore this dilemma for the simple reason that the choice between high art and commerce was never really an issue for the Renaissance poet. At that time, poetry as an art form was restricted to a wealthy, educated elite. Only a minority of people could actually read, and so a poet knew that his audience would always be very small, whether he liked it or not. Paintings, on the other hand, could be seen by a much wider audience—not least because many of them were publicly hung up in churches, where they could be observed by rich and poor, male and female, literate and illiterate alike.
https://www.poetryfoundation.org/poems/43745/andrea-del-sarto