ECC is a must-have if you want to minimize the risk of corruption, but that is true for any filesystem.

Sun (and now Oracle) officially recommended using ECC ever since it was intended to be an enterprise product running on 24/7 servers, where it makes sense that anything that is going to be cached in RAM for long periods is protected by ECC.

In that sense it was a "must-have", as business-critical functions require that guarantee.

Now that you can use ZFS on a number of operating systems, on many different architectures, even a Raspberry Pi, the business-critical-only use-case is not as prevalent.

ZFS doesn't intrinsically require ECC but it does trust that the memory functions correctly which you have the best chance of achieving by using ECC.