That's an interesting point, but in many (most?) cases productivity doesn't depend on all services being available at the same time. If one service goes down, you can usually be productive by using an alternative (e.g. if HN is down you go to Reddit, if email isn't working you catch up with Slack).
Many (I’d speculate most) workflows involve moving and referencing data across multiple applications. For example, read from a spreadsheet while writing a notion page, then send a link in Slack. If any one app is down, the task is blocked.
Software development is a rare exception to this. We’re often writing from scratch (same with designers, and some other creatives). But these are definitely the exception compared to the broader workforce.
Same concept applies for any app that’s built on top of multiple third-party vendors (increasingly common for critical dependencies of SaaS)
