Also "private space" is now available with Android 15 and can provide the same separation within a single user profile.
Different use cases. User profiles are only active when you manually switch to them, while work profiles are active _alongside_ your main profile.
So for untrusted apps that you only use occasionally and on-demand (like the myriads of travel / shopping / random services apps), user profiles are great. For apps that you want to keep in the background, such as the proprietary messaging apps that all your friends use, a work profile is much nicer.
GrapheneOS supports having a Private Space in secondary users instead of only a single one in Owner. Supporting multiple Private Spaces per user is a planned feature at which point work profiles will be fully obsolete. The remaining use case for work profiles is to have both a Private Space and work profile in the Owner user.