Noob Q: How is trezor different from storing cash under a mattress?

I.e. if you have loyal guards with guns - quite safe, whereas if you live in a hostel - no so much.This may be true of many other bitcoin storage options, but I am trying to work out why Trezor in particular is touted as such a great leap forward, when there seems to still be this massive vulnerability via /r/Bitcoin http://bit.ly/2kLRDLy