Very short range. Requires many people for every km of defended line. Overwhelmed with numbers. Drones can avoid it with altitude. Overall, an expensive soluti

Very short range. Requires many people for every km of defended line. Overwhelmed with numbers. Drones can avoid it with altitude. Overall, an expensive solution unless you happen to have thousands of bored soldiers who have nothing else to do (which is sometimes the case for some militaries).