Airbus thought they weren't necessary. At first, on the 'bus, I was sceptical. But after several thousand hours, I'm in agreement. The levers are technically a switch. You move them into the detent of the thrust regulation required, and the fact they don't move when you press a button is inconsequential. In fact, setting your thrust limit by moving a lever in the correct sense is more logical than pressing a button. (I only ever found one pilot who could explain that Boeing THR button adequately!)
And when want to use the thrust manually, they become regular thrust levers.
But the best autothrust system I've ever used was on the VC10. The Flight Engineer had his own set of thrust levers on his desk and would set the thrust, or fly a speed that you asked for. And it was proactive. On a check ride, you briefed the engineer to give you the setting you needed, which wasn't necessarily the one you asked for! The only snag was that the systrem was expensive. Some of the FEs could drink a lot of beer!