nowadays, what are the most common use-cases people using an IDP for?

Whatever a cognitive load of stream-aligned teams is :) Besides the discussion we had in another thread - at the end of this article you will find an onboarding service defined: https://khalasa.com/2023/05/symptoms-that-there-is-a-platform-missing-and-what-to-do-with-it/

Quite various: • catalog: a dev can see his service 360 in a single place: who is on call, where it is running (K8S, cloud…), recent alerts, read me and doc, API specs…. • Self service actions for devs to scaffold a new templated repo • Self service to request and deploy a cloud service (S3, database…) • View all the vulnerabilities that affect specific services in productions • Metrics to build DORA or production readiness or other scorecard initiatives I would say there are many more but those come up a lot a lot