Would you sign the deal and why?

Amanda Hocking and E.L. James did it: they signed a deal with one of the big six publishing houses after they became successful. There are more authors who signed contracts and I keep wondering why. Hocking had submitted her work for many years and kept getting rejections, and I'm sure it wasn't any different for James. Both made millions; both decided to hand their books, and with them control, rights, and money, over to a publisher. Hocking said she wanted to have more time to write instead of being tied up with marketing, and she also wanted her books to receive better editing. But surely she could have employed someone to do that for her? If you have millions why not take matters in your own hands? Of course, it's easier to sign a deal and let a publisher handle the paperbacks, hardcovers, audio books, and marketing, but if you sold so many copies, you have enough fans to carry your future projects; an announcement of an upcoming new book would be enough to have thousands of people downloading it.
Don't get me wrong, I'm not judging what they've done, I'm just wondering about the reasoning behind it. I've only sent out about 40 submissions, so I don't know how it must feel to collect rejections for years. But to be honest, even after my 'few' rejections (many of them deserved, I hasten to add) if an agent or publisher would approach me when I've already done the hard work, and I'm selling thousands and thousands of my books, I'd tell them to sod off. If they didn't believe in me back then, I don't need them to drool over my books now.
Certainly, I could keep my rights for the e-books and sign over the paperbacks, hardcovers and audio books, but I'm far too curious on how the whole process works and rather learn the tricks of the trade.
Many say they self-published in the hope to be discovered, and I wonder where their Indie pride is. Nobody would approach you if your book doesn't sell, but if it sells well enough, why would you need the help of publishing house? Someone said he'd sign the contract to satisfy his mates; it's more to be able to say a household name was interested in their work, or that they've been through the quality control process of the gate keepers. Something that doesn't bother me at all. People can think whatever they want. In fact, I believe those, who think my books are worth less just because I've self-published, would be rather surprised if they read them. I won't sign anything to please skeptics. I think it's safe to say that I'm content being a self-published author, and will continue this route.
The only contract I would sign would be a film deal, because I don't know anything about the film industry.

I'm curious how you think about this topic. Would you sign or rather stay Indie?