Why is real estate market so inefficient?

The US real estate market is really inefficient:

For decades the market has been characterized by low volumes and extortionate transaction costs (sales commissions, taxes, and mortgage fees total about 10% of the sales price). [As a result,] just 7% of American homes change hands each year (down from 20% in the 1950's).

PropTech firms are trying to take advantage of the inefficiency, helped by my former employer, the Antitrust Division of the Justice Department:

...in 2008 the Department of Justice (doj) ruled that MLS listings data could not be restricted ..., and should be shared with online platforms. Zillow and Redfin now publish MLS listings.

New entrants are bringing liquidity to the market:

These firms use vast quantities of data and whizzy machine-learning algorithms to appraise homes and make an initial offer, often within hours of a seller asking for one. A couple in Covina, in greater Los Angeles, requested an offer from Zillow on Christmas Eve 2019, had their home inspected on December 26th and accepted the bid the next day. They chose to set a closing date in March 2020, but could have opted for December 28th. ... The fee is typically around 6-7%, almost the same as a seller would pay an agent—but for a much quicker and easier process.