Containers, especially the Linux (as opposed to the FreeBSD) variant, are inherently less secure by nature than virtual machines.

Also, FYI, we sysadmin types can spin up VMs just as quickly as containers and have been able to do so for 20+ years. It’s just devs didn’t know anything about it and couldn’t control it, so they reinvented something we could already do — but poorly and very insecurely.