why can't one quit smoking?

Yes it causes diseases but it is a bad habit that when you do it you don't think of anything it is only like if you love to eat chocolate you'll eat it so for some people it is not only they need it or can't rid of it no it is enjoyful for them, some people like it's smell, it's taste and can't quit because they don't want to.

Once addicted it becomes very hard to quit. One always misses the enjoyment and pleasure they have been getting from smoking all along and consequently relapse into smoking even though they quit for a brief period of time. Therefore they cannot stay away from smokink for long.

because we like it