They are disabled due to auto farms and bugs, and no they are never going to be re-enabled again, same thing with hoppers
im just wondering, can they be added by buying features, like be able to add droppers, hoppers, and pistons?
Nope. Ignoring the bugs and lag with them. They allow automation of making money, which is economy-breaking. Gotta work for that cash.
Though I would like to see hoppers enabled which will be good for auto-smelters furnaces. Sadly not gonna happen because of income-automation issues.