About 15 years ago, I moved to a city where I didn’t know anyone. I joined Twitter because I like to try new apps as early as possible. It turned out to be a great place to talk about live music in my city, amongst other things. I met all my friends on Twitter.
At that time in my city, it was very much the town square that Elon wants it to be now. It was a place to discuss events in realtime; especially sporting events.
I suspect the advantage for Twitter was that you could communicate with people you didn’t know directly like celebrities, authors, politicians, etc. Not just write to them, but they write back because sending off a short message is much easier than making a call or writing a letter. Sometimes that is an unhealthy parasocial relationship but, it doesn’t have to be.
Kevin Smith basically started writing the movie Tusk in a collaborative way with Twitter.
I always thought of a cover letter for clarifying something on your resume. Ex: you’re changing careers or industries and out want to clarify why your experience is relevant. So, I don’t do them for every application but in certain situations.