Not every PR is a feature. There will be lots of laying groundwork. Stuff going in but not yet activated as a feature flag. Small changes often make roll back easier. Regressions easier to detect. You can blue green your little change and auto detect if it is causing latency or availability issues on 1% then 10% etc. of traffic. This means you can early detect and do easy roll backs as nothing much has changed.

Downside: your code is always a Frankenstein monster of feature flags that need to be cleared up! But hey that's more PRs to boast about.