This is absolutely true if your buying or selling a single home. But if you want accurate data for your zip code, can you get it? You can't. You only get what NAR wants you to get, which as I mentioned is not all that accurate. Even if you go look at the MLS it skips over data like seller paid for costs that are not traditional, like I mentioned. This is huge especially for new construction.
There are also other reasons to get housing data. Its a huge portion of the overall economy, the overall bond market, consumer credit, etc, etc. If I want to invest in MBS for example, I need to know where housing is going. I can go to the BLS website and find out how much just about any consumer good or service changed this month, but getting accurate picture on actual home sales price is almost impossible - at a local or national level.