It shows you several things during that time though. Al is a tough SOB, and the fact that he fought for several episodes is meant to drag out, to show you it wasn't a quick one and done thing, especially back then before lithotripsy and modern medicine. He won't be killed or knocked down no matter what. The show had focused on him so much to that point, it allowed a chance to showcase and build other characters, without Al hogging up all the screen time. But the most important thing is it showed just what a hold he had on the entire town. While he was laid up, nothing really happened around town, no deals got made, everyone knew he was holed up sick and he was still the talk of the town. IIRC Tolliver was about the only person who saw Al's illness as a chance to take advantage and act while he could, but he was new in town, looking to steal Al's customers, and make a name for himself. That half season of Al being down-but-not-out just served to cement him as the unofficial tyrant of Deadwood.