I'm still very much a newbie but your explanation has now left me in a better position than where I was when I first commented. :)

A few follow up questions:

1. They could have achieved the same using cookies too, right? How is it different from using cookies?

2. Is it better because quicker? Or is it better because local storage allows a site to store/retrieve more data from the user and thus reducing the need to get it all from the server?

3. What about CORS? How doe sthat factor in?

I honestly don't expect you to answer all these questions. you seem knowledgeable about the topic, so posted these questions here. I'd be very glad if you could simply redirect me to a relevant webpage.

Thank you for your time and efforts, I appreciate it very much!