I used to be like this, but college changed that. People in the Midwest were so randomly friendly that I eventually it wore off on me. But the thing about conversing with strangers is that even that is easier than conversing with people you do know somewhat half the time. You don't have to worry about judgment or anything else. But my mom's more or less like you and my Dad's a super extrovert. I ended up somewhere in between--more like I chill by myself and do my own thing, but when I'm out and about I'm one of the most open people there. I think it's a good balance to have. It keeps me fresh.
I have no problem talking with people I know and don't know, I'm good either way, but I don't always feel like talking it's not something I can change either

I can go with the flow a lot of the times and can adapt to situations, I just prefer to be alone when I'm not with family. I go to all sorts of parties and social events, but I don't overstay my time at them, just how I am.
I don't agree with your lions and tigers analogy though. I think spending too much time by yourself stunts your growth in the same way that not taking time for yourself to contemplate things and explore stunts your growth. Most people I know would say I do have introverted tendencies however. I tend to not show up to shyt I get invited too all the time.
Sure, if you spend 20 hours of the day by yourself then problems could arise, but at the same time there are plenty of introverts that have done great things. I mean, look at it like this a lot of your NBA titles are a result of two introverts

The fact remains though, that brain chemistry that causes some animals to roll in packs/prides while others don't is also present in humans as well, some people are just more cut out to run with a pack while others are more comfortable hunting on their own. I don't want to be alone, I
need to be alone at times, whether it's just zoning out with my headphones on in the gym like I'm the only person there or going for a drive upstate and walking a trail, it's something i need.