What happens when you need to go out of town for an extended period? If it was just another ${X}aaS, you could temporarily suspend those plant instances and avoid the charges. Their work would be unused during that period anyway, so why pay for it? On-prem would still continue to accrue those charges. Also, what happens if you have your large extended family over for the holidays? Your on-prem plants would be unable to handle the load and start returning 504 type errors. With ${X}aaS you could just spin up a few more instances or even upgrade to larger instance types. Once the family holiday nightmare is over, you just spin them down again.

Unless you use Monsanto seeds