Beyond possibly deflecting thrown vodka bottles, what are these things supposed to accomplish?
the cope cages showed up before the feb 2022 attack, without talking to actual ru personnel we wont know exactly when or why they thought it was something necessary.
but the theory among the pundits is that during the 2nd chechen war, the ru mechanized units took a lot of losses from rpg fired from overhead on multi-story buildings in urban areas. cope cages might help against a basic rpg, but does nothing against the dual charge warhead in a javelin. so it was wishful thinking at the start of the war.
nowadays a lot of armor is being disabled by mines, anti tank missiles, or artillery rockets. the crews abandon the vehicle and the ukr forces use smaller drones to drop bombs/thermite on to the top to permanently disable the vehicle if there is a chance of the russians recovering it. the cope cage could protect against those smaller drone tactics.
cheap loiter munition attacks on towed howitzers have also been defeated by basic netting. so the fact that they are factory installing the cope cages and netting indicates there may be a reason. it could just be there to protect the ir/thermal main gun sights from smaller incidental attacks and not intended to stop a javelin or gmlrs.