Not to mention that the RUC and UDA had a vested interest in selling drugs. If addiction is rampant, and is being pinned on the IRA it may turn the community on them.
https://www.spin.com/featured/inside-the-ira-spins-1994-feature/ this is a really good, unbiased article that goes into the late IRA's response to calls for peace as well as how their structure worked as a whole. This is specifically about the war in NI though, and not the bombings in England, though it talks about why they went to such a strict recruiting process.
I have an opinion on it though! DON'T! FUCK! CHILDREN!