TL;DR Prevention is better than cure, but we need both available when managing complex IT systems.

When you live near a cliff edge it is common-sense to build a fence along the edge to prevent people falling over that cliff. That said, it is also worthwhile having ambulances available to take those who do fall to hospital.

Fences are always a compromise; too low and they may as well not exist, too high and the block the view. Also, some people are insistent on climbing over fences and fences inevitably fall into disrepair over time.

What am I blathering on about fences for?

Consider your IT system, it is likely you have some proactive protections in place. Limiting access to production systems, using encryption, setting up firewalls, and so forth. These are your fences.

I would also wager that you have system failures too. When your system fails you have process and procedure for recovering the system back to an operational state. These reactive recovery process is your ambulance fleet.