Good question, MP.
First off, the TDA's work is not over... it's taken 6 Summits to get to this point, and yet there are still some areas of difference, for various reasons. And where those differences exist, the TDA would be remiss not to recognize them as house rules.
I would disagree that the TDA "consistently" refers to house rules... they are mentioned or implied in 8 of the 62 rules:
Rule 4: Electronic devices. It is just very difficult to have a standard for all the different devices out there, some venues allow headphones, some don't. Some allow tweeting at the table, some don't. Alot of this is market-specific and rather than trying to regulate it all, the TDA leaves everything beyond talking on the phone up to the house.
Rule 5: Language. The TDA at one time did have a specific rule on language (English plus the native language of the country), however foreign TDs complained that they couldn't always get enough dealers and floor staff who were native speakers so they needed flexibility on this.
Rule 14: Forward motion, mucking / betting lines, etc. Some houses use betting lines, some don't. Some use forward motion, some don't. The "default" position of the TDA is no betting line, and chips-released rather than forward motion. So house rules have to apply for those venues that use lines and/or motion.
Rule 18: Asking to See a Hand. As the subject of a recent thread on this question shows, there is still a wide range of opinion as to: A) when a request to see a hand will be honored, and when it won't; B) when cards shown by request are live, and when they're dead. The position that the entire association agrees to is that the only players who can ask to see a non-tabled hand are those who have either tabled their hand or still retain it face down. But whether the request is granted, and whether the cards are live, are still matters of house policy.
Rule 25: Deck changes on dealer push or level changes. This is a labor and management issue, so each house has to decide how frequently it does deck changes (and dealer changes) based on the specific labor conditions at that venue.
Rule 34: There are no standard agreed-upon TDA lowball rules, so house rules apply there.
Rule 38-B: Some houses kill a skipped hand if substantial action out of turn occurs, while others will limit the player to non-aggressive action. Until and unless agreement is reached on this we have to accept the differing views.
Rule 45: Allowable # raises when tourney is down to 2 players: some houses lift the limit, while others keep it, so those rules apply.
*************************************************
Hope this helps and welcome to the forum.