Backend under AGPL prevents someone hosting it as a service. AGPL specifies that hosting _is_ distribution. Therefore, anyone hosting it must do so with public code. This provides a soft form of exclusivity to run their own Cloud.

A frontend, permitting customizability, white-labeling, and so on, makes more sense to be more permissive.

Grafana is a solid example to illustrate why.

Moved from Apache to AGPLv3 in 2021 specifically so cloud providers couldn't host modified versions without contributing back, while keeping plugins Apache-licensed.