Talking to strangers is a skill. You can practice it! I've made a point of trying to practice, albeit halfheartedly, and even though it's difficult for me, because I like it when other people try to talk to me.
It is definitely something one can learn. I also like it very much. Most people are just very nice and love chatting a bit as well (just be respectful of their time and know when to bow out).
There are also other functions that purely having a good time. E.g. when you are in a train with reserved seats, striking op a conversation is also a good way of gauging whether it's ok to leave your bags when you leave your seat to grab a drink or some food. Also, people feel more responsible looking after your stuff once you have socialized a bit.
For me it's not super-difficult. I came from a small village where it is normal to greet people and maybe chat, even if you don't know them.