I do some AI agent work; I suspect it's because there's a lot of people with infrastructure and programming skills that are new to building "agents". It's easy to think this requires monolithic architecture when a distributed DAG is often optimal. A lot of frameworks and SDKs for "agents" also inadvertently encourage monolithic design.

Long way of saying it's the marketing machine doing its thing. This looks like Cloud or run it yourself DAG software with some bells and whistles.