Many supermarkets offer this functionality, but the products are collected by humans. It would be tricky to implement a robotic system that you could maintain a

Many supermarkets offer this functionality, but the products are collected by humans. It would be tricky to implement a robotic system that you could maintain and operate for less than minimum wage. There's also the additional problem of what to do if they don't have the specific thing you asked for. Finding a 'reasonable replacement' is actually a nontrivial problem for AI to solve.