The simple answer is, because we don't have to, because that's the way English is.
The first case is different from the others. In the first case "long hours" is not the object of the verb, but an adjunct: an adverbial expression. With a particular time, "for" is optional ("I worked three hours" or "I worked for three hours"); but "to work long hours" is an idiom, and "I worked for long hours" sounds odd.
In the other cases, the phrase in question is the object of the verb. In its central meanings, "work" is intransitive; but it has quite a few special meanings where it is transitive, and these are examples.
"Work the clubs" is an idiom in the entertainment world, meaning to go around the clubs (nightclubs, comedy clubs, social clubs) performing in each: there is an implication that it is hard work, for not much pay. I think you could substitute different kinds of places or events for "clubs" ("work the festivals", for example) but you wouldn't say "He worked a club" - it refers to the continuing experience.
"Working a drug case" and "Working a cone" are examples of its transitive use in the general sense of "do a
job".
