How many series do you watch purely due to who is in it?
There's been a few but admittedly not that many.
This is Marketing 101. As a general rule, you want to have at least one well known actor in your new show/movie in order to attract your initial audience. People will either stay with the show or dump it if they don't like it anyway but you want to have at least some name recognition with the cast in order to bring in the initial crowd. There are certain actors who have proven themselves to be a draw regardless of what type of film or show they are in.
Honestly, I think that is anicent and outdated marketing for TV shows, Espesially streaming services like Netflix.
Social buzz and word of mouth is the new marketing trends.
A Game of Thrones would have been just as huge without Sean Bean in the first season. And it's grown from season to season after beheading him. Shows like Vikings, Big Bang Theory, Grimm, Lucifer have been getting renewals without big stars (granted, Grimm was cancelled after 5 seasons, but that is an eternity in today's TV world).