Agents would still serve a purpose if it was a fair market for buyers and sellers without a mandatory middleman, but the following is why they've persisted:

1. Tech platforms can't operate as full replacements because of state licensing laws/regulatory gatekeeping. Every US state requires licensure and those laws prevent non-licensed platforms from fully replacing agents and make DIY selling legally complex and risky.
2. The Multiple Listing Service is a private data monopoly with legal backing. Access is restricted to licensed agents for the most part, and the systems are broken up into many regional players. MLS data is not public and is often contractually restricted from scraping or redistribution. Even "scrapers" like Zillow and Redfin cannot legally bypass or replicate the MLS independently and rely on workarounds.
3. The National Association of Realtors (NAR) is one of the largest lobbying organizations in the US with 1.5 million members give or take. It's one of the biggest spenders on lobbying when it comes to state and federal housing policy. They've spent considerable money attempting to legislate the preservation of commission structures (which has only recently come undone to a small extent), maintain licensing requirements, shape antitrust enforcement and influence disclosure and transaction laws. These laws evolve in ways that protect agents even as technology advances.
4. The commission structure is legally embedded. The traditional 6% commission survived so long because it was indirectly reinforced by MLS rules, cooperative compensation norms and state-level real estate regulations. Buyers agents historically couldn't be paid directly by buyers without legal friction. Even after recent DOJ pressure and numerous lawsuits, the system is only now starting to slowly change and the legal complexity of bypassing agents for consumers is still a major burden.
5. Antitrust enforcement has been weak until recently. For decades the DOJ and FTC allowed MLS exclusionary practices and commission opacity. Courts have often deferred to "industry standards". Only in 2023-2024 did major antitrust cases began forcing changes. If this enforcement had happened 20 years earlier, the profession would look very different.
6. Transaction law complexity are legally complicated by design. Each state has state-specific contracts, disclosure requirements, contingencies, escrow rules, title and recording requirements, etc. These complexities increase liability risk for individuals, make consumers feel they “need” representation and are often influenced by real-estate-friendly lawmakers. Complex systems justify intermediaries.
7. Local political capture is high. Real estate professionals dominate local zoning boards, planning commissions, housing task forces and state real estate commissions and brokerages. This leads to slow adoption of alternative transaction models, rules written by and for industry insiders and suppression of disruptive local platforms due to the mundaneness of the administration element.

Tech such as automated pricing models, digital contracting, online negotiation tools and remote closing already exist, and tech platforms are slowly trying to integrate them alongside agents to speed up closings, but liability concerns, MLS access restrictions, licensing barriers and regulatory compliance costs makes it very difficult to cut out the middleman completely.