Removing tools removes unnecessary options.
Look at films. Scorsese, John Woo, Wes Anderson. The best cinematographic styles come from a reduced number of cameras, lenses and lights.
Being selective and curating your own toolbox makes decisions faster and easier. You're saying, "I'll decide on the right tools up-front so I don't have to think about it constantly." It's a type of minimalism.
Your remaining decisions become clearer. You focus on more important things like the angle, the subject and the message.
With startups it's the same. Pick a small set of tools, for internal communication, marketing, organizing documents, so that when you roll out, you're not scrambling. Decisions about marketing, product, and deployment are focused around what actually matters.
When you have to think fast, you can hone in on the opportunity at hand.