Americans will never be able to figure this out.
It makes sense, but honestly roundabout driving techniques still cover a massive spectrum here. You've got the timids who are way to slow and you've got the aggressives who can be unpredictable. The former doesn't have the capacity to indicate because they don't know what they're doing yet and the latter doesn't have time to indicate because by the time anybody else can process what they might be doing they've already done it and are gone. Surprisingly few people fit in a happy medium, I swear it's a reverse bell curve. Like
@Exorcet says, it probably does make our roundabouts a bit more intense than other parts of the world where decent etiquette is more widely known.
So far I haven't used my indicator at all. Not much time is spent in our little roundybouts and I don't think anybody would process it correctly anyway. I go in, I go out, and hopefully nobody else screws that up. Just ten more seconds without totalling my car, please.