It's much much much easier to cook up a solution for internal use than to create a product for external use that you can sell and that caters to your customers whims and that reasonably easy to use without requiring direct access to the engineering team for support.
You're right, but for $173mm in funding, you'd think you could build a product for external users that's at least feature parity with a "cooked up" internal project.
What's kind of incredible too is they actually lose money still.
The losses are growing faster than the revenue.
They've only had, what, 14 years to figure this out?
You wonder what their staff of 1000ish are working on.
Also, forgot this gem: "On January 21, 2023 PagerDuty CEO Tejada's layoff memo was criticized for insensitivity for inappropriately quoting Martin Luther King, announcing promotions of executives, and tone deafness." (from wiki)