No, obviously you can. You're confusing the bits covered by a signature with the real-world interpretation of those bits.

Good luck buying a slice of pizza with bitcoin.

In Zimbabwe you can.

Sometimes I wonder what percentage of the people talking about all the things one can do with bitcoin in Zimbabwe have been to Zimbabwe and done those things.

In this case I was the child of my parent. But given that people over there are selling their cattle with bitcoins it seems not too far off.

Are they transacting in bitcoin, or simply using bitcoin as a device to evade capital controls? There are lots of ways to get around capital controls, and bitcoin may very well be an effective way to do that, but that's not evidence of bitcoin's utility as a mainstream currency.