ok ok. I sorta get that. But shouldn't drugs be awful? Honestly, I'd rather not even play with them in the game. Personal preference. But since they are part of the game, make people check during use. Also, won't be any addiction checks for things like foci and stuff. That's silly in my campaign world. 
Some drugs come with after-effects though. For example, Cram makes you take damage when it wars off, Jazz disorients you, and so on. Psyche is pretty much the only drug without penalties during or after use, aside from the behaviour impact. And Jazz&Nitro pretty much come without a chance to avoid all addiction tests.
And I actually quite like addiction checks for people using more Focus Rating than their Magic Rating at the same time. It's one of the balancing factors in foci use, for starters. It also only kicks in at high Foci amounts AND, unless your mage constantly overdoes it, will only matter at Force 9+ in total active at the same time.