Specifically almost all operational areas have an up time KPI. Changes especially frequent changes present a risk to up time. Most if not all operational managers are have a pay component tied to uptime/availability.
You say this like it's a bad thing. For many things, operational uptime is related to production capacity - if a server goes down, production can go down. It's where the "we lose a million dollars a minute" stuff comes from. Operations goal is to keep the service running so that doesn't happen.
It's where redundancy, staged rollouts and other things are done which limit downtime due to hardware failure, software bugs, etc.
(It's also a HUGE PITA to do because during a staged rollout, you have to deal with both old and new schemas of data because not all the data is upgraded at the same time. In fact, in most rollouts, you update the code to handle the new data schema first, then code to switch between schemas, code to write data in both schemas, then your new code that required the new schema, then retire the old schema and handling everything with the new).
And yes, it makes PaaS/SaaS much harder to deal with because you need to do a staged rollout, but SaaS/PaaS don't like that because having to deal with old/new data schemas is a lot of work over just switching everything over at once.
But the goal is there because downtime can cost a lot of money very quickly and it's operations job to figure out all the possible risks that lead to downtime, their costs to the business if it happens, the chance of occurance and then mitigations. Some mitigations are ignored - if it only happens once every 10 years and costs a billion dollars to mitigate, it might be something you recognize and do your best to work around - if you can get things running back in under 1000 minutes (at a million dollars a minute), That's 16 hours 40 minutes, then it's cheaper to not mitigate it and just do what you can to recover from it.
Some operations are also such that there can be ripple effects in the economy. Say, if Visa or MasterCard went down for even an hour how much chaos will be caused. (And yes, they do go down, but there are mitigation that let it be unseen for operations).