There were good points brought up by both D_Fosse (nondestructive spot healing is already available in Lightroom Classic and Adobe Camera Raw), and PECourtejoie (it could take a lot of computing power).
Any type of nondestructive editing can require more processing power and memory because the application always has to be ready to re-render all affected objects into final pixels whenever you change something. Using Smart Objects definitely increases the load on the CPU and RAM. The nondestructive spot healing available in Lightroom Classic and Adobe Camera Raw works, but anyone who uses it a lot knows that it is by far the slowest tool in those programs. And the more spots you paint, the slower it gets. If Adobe figures out how to GPU-accelerate the nondestructive spot healing in LR and ACR, maybe that will be the time when nondestructive spot healing will be more practical to have in Photoshop itself. But not yet.
By the way, that leads to one workaround for this: Select the layers in Photoshop, convert them into a Smart Object, choose Filter > Camera Raw Filter, and use the Spot Removal tool in the Camera Raw Filter. It will work on the Smart Object, and you can still open the Smart Object to edit the individual layers.