Why Does John Zeratsky Compare New Software Tools to Debt?

On Rocketship.fm's Making Time, John Zeratsky, co-author of Make Time with Jake Knapp, says each new platform a team adopts is like debt. The payment comes due every day or every hour. Debt is not automatically bad. It lets you buy what you could not otherwise. It turns dangerous when you never get the benefit and you are stuck paying. Tools meant to make a team productive can do the reverse. He wants as few as possible: Slack inside the company and email outside, or Google Sheets instead of a heavy project app. A leader's "let's try this" is cheap for the executive and expensive for everyone who then has to live in the tool.