They already do that. There are weight and position sensors in the passenger seat that will disable the airbag if it detects an object under certain weight and height parameters. The airbag won’t go off if the seat is empty either. If you want a simple example, put a 40lb box of paper or books in the passenger seat and buckle the seat belt. You’ll see that the light on the dash will indicate the passenger airbag is off. I could describe how the system works in more detail, but if your genuinely interested, Im sure there are some good resources on the internet that explain it better than I would.

Most cars do this based on weight.