Comment by ggregoire

I think it's more about avoiding downtime (I just upgraded a pg with 1TB of data from v11 to v16 and I didn't notice any breaking changes). In an ideal world, every client of the DB should be able to handle the case where the DB is down and patiently wait for the DB to come back to keep doing its job. But from my experience, it's rarely the case, there is always at least 1 micro service running somewhere in the cloud that everybody forgot about that will just crash if the DB is down, which could mean losing data.