They take 6% out of most housing transactions and add very little value. They managed to put themselves in the critical path by lobbying and regulatory capture. You don't get access to the listings and MLS open houses unless you go with a realtor. They also made the process artificially complex.
Most other countries seem to rely on direct customer to customer for most transactions, with a notary making sure the contracts are binding. Why can we not do that in the US?