Comment by Pasorrijer

Good question! A few reasons. Weight and balance is super important so anything you add means something else needs to be added or balanced. Power requirements are also a problem. More electronics means more power maybe means new engines. Maybe that all means more weight, so you need to reinforce the structure. Which means you're heavier and need a better engine. Etc. Sensors can't just be installed, if you need to drill holes and break pressure bulkheads.