I can't speak for general life, but as far as social groups go, I noticed ENTJs seem to "accidentally" take the lead.
Example: my friend Kevin would occasionally join my primary social group on our outings at college. As we were friends before college, he knew me best and we were close friends, so it always ended up being just me and him talking on the way to our destination. The interesting thing is that, as we were always in front of everyone else, we ended up being the de facto leaders and making the group's decisions... even though I was a small part of the group and he wasn't even a part of that particular group.
My experience with other ENTJs has been much the same, with respect to social settings.
I think in a lot of ways ENTJs just have this management attitude about them. Even if they're not "trying" (though I don't know of a time when Kevin wasn't trying to manage something), they still tend to make the journey to the 'top' relatively quickly. It's interesting to observe them do it. In situations where they're "active" (I assume them all active, but I know not all of them will be), they know what needs to be done, and they do it with the upmost precision.
Oddly, though I have more experience with INTJs, I couldn't tell much about their leadership abilities. My younger INTJ cousin has also been my best friend for years... yet in almost everything we do, I take the lead. He makes me. In other situations (i.e. those where I'm not involved), he will quickly be front and center and very decisive on matters. My older INTJ cousin is similar, but with minor differences: he lets me take the lead until he determines that it's time to step in and be decisive.
The count: one INTJ steps aside for me, takes the lead elsewhere. One INTJ steps aside for me, but takes the lead when necessary.
By 'steps aside for me', I mean they put me in leadership position for whatever reason, almost every time. Not implying superiority or what have you.
I think INTJs just like experimenting. Seeing how the approach of some people goes and either 1) acting on a similar approach or 2) making adjustments to said approach where necessary mid-approach. There's no reason why either of them (both more capable than I) would put me as leader unless they were getting something out of it.