I actually don't enjoy loss of control. I enjoy the illusion of loss of control and the feeling of helplessness. But feeling helpless and actually being helpless are two very different things. I would find an actual loss of control completely traumatic. Getting tied and tickled, with a safeword, allows you to experience the feeling of a loss of control without actually ever being out of control. That's why I'd never be tickled by anyone I wasn't deeply in love with or whom I didn't trust completely.
I do think a rollercoaster is a similar thing. It provides you the feeling that your body and safety are at risk while also giving you the peace of mind that you will be okay when it's all over. This is a neat thing to experience. Sure, the rollercoaster could crash and kill everyone, and sure, you could possibly stroke out or something while getting tickled, but it isn't very likely. Most of us go into these situations knowing we will be fine.
For me, getting tickled by someone you don't trust, or with the intentions of pure torture with no safewords, all of that would be more like riding passenger on a wild car chase or some other situation where safety is not guaranteed. Not arousing to me.