Their sole purpose is to extract money from you. They're businesses, that is their business model.
The value they provide in return is rather minimal - unless getting e-mail out is at the very core of your business and you need to pull every last string to absolutely maximize it.
Otherwise there are cheaper ways to get reasonable deliverability even at AOL and Hotmail. The default deliverability is already quite good, which is what services like SendGrid largely bargain on. I firmly doubt SendGrid signs each of their customers up for the aforementioned whitelists. They probably offer "assistance" with the process, which probably amounts to sending you a link to a nice HowTo document, and which probably yields them a small affiliate kickback when you actually follow through.