[richthegeek]

Often "impossible" is based on constraints like "0 downtime" "100% planned rollout, rollback scenarios" etc.

These constraints get thrown to the wind when the downtime is already happening.

[pclmulqdq]

I was being a bit hyperbolic, but this is the real reason. However, the VPs in question often have the authority to approve changes that don't have rollback scenarios (for example), they just don't until the shit hits the fan.