I'm not sure what that has to do with Singularity?

I know that the HPC clusters I've used in the past few years have all supported Singularity, but none have supported Docker (aside from our small lab cluster). Many HPC admins are (understandably) hesitant to allow non-admins access to start Docker containers (requiring root), but Singularity has no such user permission issues -- and it's faster than initializing a full VM to run a job. I don't expect that to change so long as starting a container requires root-effective permissions.

I suspect that many data scientists will be in a similar situation w.r.t HPC clusters (except for those that are using custom clouds like Seven Bridges).