The trendy thing in the last few years has been to move to self-publishing. Many have done it successfully. The success of Steam was initially a blessing for self-publishing. But with the exponential growth in games published, it is becoming ever harder to shine through. In 2012 379 games were released on Steam. In 2016, that number has increased to 4207.
Maybe events like flying a dozen journalist to norther Sweden drive cars in the snow and play video games like Bandai Namco, or offer tasty macarons in Paris and the possibility to meet all your developers like Focus Home, will become more important as the avalanche of new games becomes ever deafening.
Focus Home Interactive event in Paris
On console it might be even more important to have a big publisher that can get you displayed up-front on the stores.
I recently looked browsed to pre-orders on my PS4 and the games that were displayed were from Square Enix, Bandai Namco, EA, Activision and 1 indy title. Maybe a coincidence, but it seems to me it sure helps to have a big name publisher when you want to reach console gamers.