Of course it's material. If a provider has a 0.001% chance of losing some of my data in a year, I'm an idiot for not having backups. If a provider has a 10% chance of losing some of my data in a year, I'm an idiot for not having backups and for using that provider.
GMail is (usually) not an enterprise product and not a paid service, and provides no reliability guarantees. And yet it seems to be pretty damn good in practice.
I believe since then they had similar events but were always able to restore from tape. So GMail definitely has proper backups, even for free accounts (maybe not tape anymore, not sure).
The rarity is immaterial, the responsibility for data protection lies with you, not them.