I haven't been playing much, but why am I almost ALWAYS getting my secondary role?

Ever since I stopped playing ranked at the end of May (and only popping in to stop from decaying or when I feel like it), I've been queuing Mid/Jungle.

I've gotten jungle 7 out of 9 games, or 77.778% of the time.

My teammates are already at enough of a disadvantage having a person on their team who really hasn't been playing ranked lately. Why is it they get that player in their secondary role instead of their primary too?

In those games, I'm actually 2W 0L mid 1W 5L 1 remake jungle

I thought there was some distributional thing showing that people got their primary the majority of the time. I'm nowhere close to that. I understand that my sample is small, but seriously. It really doesn't encourage someone to get back into playing ranked when they don't get their main role even 25% of the time...