I think a lot of it has to do with scale and the ease at which that scale can be increased (and in some cases monetised). Some of it also has to do with mitigating risk as it's easier to manage what happens in a container as opposed to just letting an agent roam free.

What I really take issue with though is that a lot of the solutions only support a containerised approach, I'd much prefer they start from a general "agent" that can also run containers (et al) rather than hard coupling to one technology.