There are many ways a person can grow. While society rewards the extrovert, everyone growing in the direction of being more extroverted isn’t great advice.
You mention seeking discomfort. A pop-in isn’t seeking, it’s finding me at my doorstep. I seek discomfort by taking solo trips to various countries around the world. It’s a planned trip, sure, but it pushes me way outside my comfort zone and forces me into spontaneous and unexpected situations each day I’m away. Other than the flight and hotel, I don’t plan much and just see what happens. The same goes for various other things I seek out. In my home, I want to be able to relax without having to think about what may or may not randomly show up.
While humans need variety in their life, they also need some sense of stability. Where people choose to get those things is going to look different for everyone. This is the fact of life.
I know families who have a door is always open policy, then rent the same cabin for vacation every year for decades. I do the opposite, and they wouldn’t dream of attempting what I do. We are both meeting our needs, just in different ways. One could say their door always open policy is their attempt to remain in their comfort zone. They can feel social and have little doses of surprise, all from the comfort and safety of their home. If that is enough variety for them, that’s great.
My sister has a door always open policy with me, but I still always text first. I don’t want to show up and find an empty house, or that they’re all in a mad rush to finish a big school project before Monday, where I’d be a distraction. It doesn’t have to be a “schedule”, but simply a heads up and an acknowledgment that I won’t be causing an inconvenience.