Of course they don't want you to deactivate your account. It's their business to try to retain their members/customers, just like every other company in the world. Now if they are pretending to deactivate your account but leaving it accessible to others, or other shenanigans, then we've something to talk about. But this? Big deal.
I don't really know what their business plan will be, but I'm sure it won't involve normal users paying any money. So they have to make money off of me somehow, whether it is through targeted advertising or selling information to marketers. The current privacy policy allows them to give information from your profile to third parties as long as you cannot be personally identified.
So while I'm not saying they will do anything unethical, an inactive account is probably worth a lot more than a deactivated account.