People have been reselling containers without needing an intermediary VM abstraction forever; look at any cheap VPS host offering OpenVZ-based "virtual machines"—which are actually [resource-quota'ed] containers.
It's not a question of need; it's a question of ease of opportunity. It's now easier to virtualize via container, and there are more opportunities, since it's easier to get a VM than a dedicated server with hypervisor access.
