A bit from an ops-side, but I think it applies. I think pair-work, pair-programming, pair-troubleshooting is a tool for specific situations. It's amazing in some places, and an exhausting waste of company resources in other places.

Like, if we're in a hard situation with many unknowns and possibly horrible consequences of mistakes. Critical systems down, situation is weird. Or, implementing config management for something entirely new. Or, trying out new code structures, ideas. That's when being two is great. You can bounce changes you make to the system off of your copilot, so you can be very safe while being fast. You can have two opinions about shaping a piece of code and APIs. You can iterate very quickly if necessary.

On the other hand though, there are things that require deep thought. Like, I had to figure out how 4-5 teams use an infrastructural component, what's the live cycle of the component, when to create it, when to delete it, how to remove it. It ended up being twelve lines of code in the end, but like 1 phone call every two lines of code, and an hour of thinking per line of code. Pair programming would not have been compatible with this.

Or, the third kind, is crunch work. The best way to do crunch work (besides automating it) is to just put up headphones, find flow and hammer it down. Have it reviewed later if necessary. But why would we need 2 guys following the same runbook for the upteemth time?

It's a great tool to share knowledge and to handle critical tasks with high error potential and I wouldn't want to miss it for that. But it can be overused in my book.