If writer A, and artist B, are working on title C, and random chance foottraffic lookiloos are D, when A, B, C and D are mutually exclusive, that is a lot of customers these four elements can attract.
If you have a title no one has heard of, written by an unknown and draw by a fresh face in the market, that means that all you can rely on is D and pray they start some buzz.
Then you have problems inclusiveness.
If A, B and C have the same identical loyalist fanbase, then you're anticipating the same readers counted 3 times to support the books sales, which means that there's absolutely no point putting those three together if any one of them would generate the same numbers as the three elements combined.
This was explained to me in the 80s as the John Byrne Effect. There were 60 thousand comic book readers that followed Byrne. No matter what he was drawing they bought it. Always. If a book is doing bad, you stick John Byrne's 60 thousand on task and boost the titles numbers... Well, 60 thousand LESS howeversomany of that 60 thousand who were already buying the book you just chained John to.
Then why do we have Jim Lee and Geoff Johns, or Jim Lee and Scott Snyder, or Scott Snyder and Greg Capullo?
When C is strong (The title). You have a book that is so beloved and so well marketed, that it almost doesn't matter who writes and draws it... But you do have to worry about brand marginalism. That if you put a talentless asshole hack on home plate for a bat with a sure thing, the title is going to tank and you've lost the only book that was generating good numbers.
Nurturing something that works is often as important as growing new products to stuff vacuums.