I could have written the above post myself, as it reflects my own experience.
Not being able to view the actual welcome page, I don't know if newcomers are able to choose not to have a welcome started. I had assumed it was a selected choice and was surprised at the dropout rate. Of course it should be optional, and the option offer should state that messaging will be involved and allow a non-English preference to be input.
I play rated games, so that if they win their rating gets a positive start, and at my playing standard they usually win if they play out the game. If they make three moves and disappear I get a few points, so it's swings and roundabouts for me.