Being "realistic" about "how long it takes to get your network back up and running" when it comes to a restoring/rebuilding/replacing a server is key. Doesn't have to be something as drastic as a server catching fire...but you know sometimes an old server, out of warranty, major component failure, or power surge has you questioning how many parts got roached. Can be days until they're back up and running again.
Or a client with several servers, having a Datto can ease MSP costs and project labor, allowing you to perform easier server migrations. We've used a Datto soooo many times to do P2V migrations.
One time a client of mine got ransomwared. I was on vacation....when I got the call, family out on a boat in lake Winnie in New Hampshire. Thanks to the clients Datto Siris S3000, had them back up within an hour, my laptop tethered to my phone from out in the middle of a huge lake.
I can't tell you how many times I've quickly done file/folder restores within minutes from a Datto while traveling, just stop for a few minutes, tether to phone, drill in, restore. The ease for the MSP is huge!