That's entirely your choice/responsibility and nothing to do with giffgaff or any other network provider. Like I said I'm sorry you find yourself in a pickle because of the outage today but there's nobody to blame for that other than yourself given you choose not to have a backup provision as standard or to procure one now the proverbial has hit the fan.
I too rely on mobile, and I'm sitting here with three SIM cards:
Vodafone: unlimited minutes and texts, 80GB data
Smarty: unlimited minutes and texts, 8GB data
giffgaff: inactive but soon to be unlimited minutes and texts, 20GB data.
The Smarty and giffgaff backups to my Vodafone connection are both provided at zero cost to myself thanks to the "payback" both networks give.