Companies and governments producing all sorts of weapons do not stop production of newer weapons. They are very big and very influential businesses. The big stocks of old weapons create problems and opportunities at the same time. To sell such old weapons there must violence that makes purchases of any weapons a necessity. Peace is an unproductive environment for the weapons-producing companies and governments.
The marketing tactics of old weapons is obviously undeclared. If you have one thousand old piece of weapon then you must give away a hundred of them to bandits. The rest of this stock will be definitely bought by the poor government where those bandits cause havoc. This is exactly how groups like Boko Haram in and around Nigeria are getting advanced weapons and that is why the Government of Nigeria are buying weapons and give away their oil revenues and sovereignty for peanuts. This is exactly the same around Israel; in Syria; in DR Congo; Ukraine; Libya; Gulf Arab states; South America; and South East Asia.
Terrorist groups and illegitimate rebels do not get weapons and money from heaven. They are just Western tools for marketing old stocks and avoid peace that will make them rot and bankrupt.
Europeans weapon businesses (White race in Europe; USA; Africa; and the rest of the World) are the sources of all such horrendous evils. Violence; wars; and fake revolutions or “springs” are businesses; and business is good. Getting free or cheap weapons entice any fool to start endless spiral of modern slavery.