Tbh, I don't know, I don't like chatting to strangers either, but when a stranger asks how my day is, or how the weather is, I assume they don't really care. Which means I can lie to them to wrap it up if I want. The level of care is probably proportional to the closeness? Small talk with partner == important, care a lot, small talk with neighbour == less important, less care, small talk with stranger == not important, no care?

I also care about the "how was your day" convo with my partner, but I consider it small talk as there is usually nothing critically important about it. Its not gonna result in a major financial or life decision 99% of the time.