One joint of good quality bud is equivalent to a bottle of distilled beverage, not to one drink. In general, you would expect a joint, like a bottle, to be shared among several people, unless the user's aim is to get "totally wasted".

Also, I think you will find that there are very few people who feel the need to sit alone and get high; mostly, users feel a desire (NOT a need)  to go to parties and get high in company.