Not a stupid question. These products tend to offer a lot more functionality and flexibility in terms of how you consume your data. Different analysis possibilities, fancy ML models, custom dashboards, etc.

Also more control over how the data is ingested (sampling or not, etc.)

These products feel more suited to teams building rich apps/webapps where as GA seems to have its roots in sites that are more "content-based" (news sites, etc.).

And for many, not sending the data to Google is an advantage in and of itself.