The folks that write the codes are plumbers of course and when plumbing was first introduced to in door and it developed, those plumbers over the years realized that changes could be made with better results the code gets re written because of many factors larger homes more bathrooms larger tub showers etc, size of pipes matter a great deal in venting issues, the problem is that most people misunderstand the true function of a vent, and just a heads up, very soon there will be a no vent system introduced to the plumbing industry figure that.
As for the DYI ers that post here most are good nature d folks looking to go in the right direction with little home improvement job and that's why i spend my time along with all the other professionals that post for the DYI ers giving advise in good will. BUT then you have THAT one person,,glues together two pieces of pipe and thinks that he's mastered the plumbing trade, and in his mind he's now knowledgeable enough to challenge the plumbers,and why would anybody pay a plumber that much money when anybody can do plumbing.. challenges are usually with sarcastic remark on a post or an answer. when i ask a question its for a reason and the reason is to be able to give him or her the most accurate answer to their question. and in my experience people like this usually end up doing things the way they seem fit blowing off the multiple advise in the posts and in doing so the Code gets butchered, who pays,, well may be a new home owner that just bought the mess the other jerk mastered up ,a tenant with nothing but problems. or a plumber that gets a cable caught in the line because it was piped in wrong. i have some sympathy OPPS NONE for this type of DIY person i be leave they deserve every thing they get. :clap: