What advantages are there to painting the inside of the block?

I have the inside of my 408 coated with Glyptal. When I sent the block to the machine shop, my machinist suggested it. He baked the block to burn out the oil in the porousity of the block and I took it home to paint it before the machine was done. That was 15 years ago and it still looks good. I can't say how much it affects the oil drain back, but it may help with it.