I've noticed an increase to pretty much 100% reliability in storage since Apple moved to SSDs instead of mechanical hard drives. We have several labs full of iMacs and numerous Macbooks in our department and there have been zero SSD storage failures.
I think the reason Apple has gone this way is because their SSDs are reliable enough that storage failure is no longer a real concern. They probably use high quality flash storage and overprovision the drives enough that it's just not an issue anymore like it was with spinning rust. They certainly charge enough for it!
My main issue is it's not just the SSD which has to be reliable. Now ANY failure basically means the data is lost.
This has just caused me to rethink my storage paradigm. Now, I will go for less storage and invest in the QNAP TB3 NAS and external SSDs. The access speeds of TB3, USB3, and 10Gb Ethernet make it functionally fast enough.
Now, the system storage is just that, my data will be external.