I don't pretend I know what I'm talking about... but from what I've heard, you are correct. They are basically only for people who want their car to roll slowly down the road with exactly the look they want, but don't want to push their car in terms of performance.
I kept seeing people on this board tell people that adapters are "NOT AN OPTION". So I did a quick google search and almost all the results, regardless of what site it was on, said the exact same thing haha.
I'd be interested in WHY they aren't safe however. That much I did't bother looking into.