If they made their tools AGPL, they themselves couldn’t build a cloud offering with additional, closed-source features.
The reason AGPL isn't being adopted in these situations is that it doesn't sufficiently protect against someone doing what e.g. AWS repeatedly does - turning open-source projects into services and then dominating the market while continuing to benefit from the upstream project. See the ElasticSearch licence change for a prominent example.
inbound=outbound license terms is a good norm for FOSS. Why should a software vendor play by different rules than everyone else when it comes to things like copyleft compliance?
[1] https://meshedinsights.com/2021/06/14/legally-ignoring-the-l...
[1] https://sfconservancy.org/copyleft-compliance/principles.htm...