Amazon Publishing switched to offering this. Now HarperCollins:
“In another move to compete with Amazon, HarperCollins announced that as of August 1, authors who sign with Impulse will receive monthly royalties. ‘There is a true financial benefit to signing with our Impulse imprints,’ said Liate Stehlik, SVP and publisher of William Morrow. Amazon Publishing recently started offering monthly royalty payments to its authors.”
There are handful of things I expect to see change in order to properly compete with the benefits that the new distribution system is offering, this is one of them.