Basil, I understand your point and it actually doesn't bother me. However, vaping is technically not allowed (though nor is reading the paper on the iPad, but The Times in paper format is fine. Go figure!) just getting it out and starting puffing is not great CRM.
Thankfully unlike my time at sea nobody actually smokes on he flight deck (smoking was verboten then too but everyone ignored it.)
To be honest, half the problem is airlines banning things to show how "robust" their procedures are in introducing entirely unworkable procedures. One Loco bans all non-operational chat from start of push to ToC and ToD to the gate. Hardly a workable procedure - if you ask your colleague how they're feeling at Fl355 you are now in breach of company procedures!