People are working on that [1]. In some sense, it's a step back to analog computing. Add/multiply is possible to do directly in memory with voltages, but it's less versatile (and stable) than digital computing. So you can't do all calculations in a neural network that way, meaning some digital components will always be necessary. But I'm pretty sure analog will make a comeback for AI chips sooner or later.
[1] https://www.nature.com/articles/s41586-023-06337-5