Also, if anyone can recommend scholarly books or journals on the topic to gain more understanding, that would be appreciated!

Just a quick fore-note, i am not a historian i just have a love of history and wish to contribute.

The quick answer is that it was a way of demonstrating power and wealth; commissioning someone to paint a large fresco was rather expensive and if you had, say, 5 of them just sitting around your home you most likely had a great deal of money that you could spend on such things. It was essentially bragging that you had the biggest, shiniest stuff. This became especially prevalent after the late fifteenth century when a lot of the commissions began coming from individuals rather then from organizations. Families such as the Medicis of Florence who had become bankers began looking for things to do with their money and couple this with a rise in secular thought, and you have a good deal of people putting their money into material possessions such as the arts.

Source: A history of Western Society since 1300 (8th edition) by John P.McKay

Hope this helps!