It can be a big deal if you're seeking to build a following to spam with updates about ongoing development / new titles. Which can have a huge impact on how successful your launches on stores like Steam are.
These days I suspect it's more common to lean on Twitch streaming of the development process to build a following. But that probably reaches a different demographic than regular twitter updates would.
Surely being on Steam is much more important than being on Twitter. I play a ton of indie games but have never used Twitter and even if I did use it can't imagine looking for new games to play there.
We do not use Twitter to present the game directly to players, but rather as a networking platform. We are looking for Youtubers, streamers and journalists there, who in turn are looking for new content there.
The thing is that Steam and other platforms use the amount of interest early on as a sign on how to promote the game. So a game just published with 50 purchases the first few hours, will get promoted to more gamers than a game with the same amount of sales spread over a longer time. Therefore it can be important to build a semi-big following on other platforms before release, to give that initial boost in the beginning.
These days I suspect it's more common to lean on Twitch streaming of the development process to build a following. But that probably reaches a different demographic than regular twitter updates would.