There is a noticeable difference having agents as a buffer when buying or selling a home. For many it is an emotional experience and without representation the sale would not close. There is also a difference between transactions where everyone is represented by an attorney who is paid even if the deal falls through, or where they are represented by agents who are only paid when the deal closes. Having a financial incentive to have everyone represented is overall a positive.
In the US the realtors recommend repairs or other changes before listing the home, sometimes handle staging the home, arrange a professional photographer, pull data for comparable recently sold homes, call the listing agent on pending home for sale to get the contract price(likely will be closed by the time the appraisal is happening) and have knowledge of the local market to help you decide on the list price. After listing a home they handle showings and setting up the lockbox, and this includes screening potential buyers, usually requiring that they have a mortgage pre approved before viewing a home. Really the buyers agent is doing most of the work showing homes. In many cases the listing agent will hold an open house to get more people to view the home, but this is more for the agents benefit than the seller. After getting an offer the listing agent still has a lot of work. They will negotiate counter offers. They will help with preparing the required disclosures. There is a lot of following up with third parties, the loan officer at the bank, making sure an appraisal is scheduled, being present with the home inspector, following up with the buyers agent to get contingency releases, negotiating repair requests or other amendments. Then there is last minute stuff that needs to be done, driving a contract somewhere to get a wet signature the day before closing, getting the county to confirm a deed was recorded today, so escrow can be released before 5pm.
Buyers agents are used in the UK too, mainly by the wealthy. Less well off clients go without because they cannot afford it and still make a competitive offer. 1% is on the low end, and it does not include VAT. If you go with a full service estate agent they are charging 2.5%, and you are paying 3% out of pocket for a buyers agent. 1.5%, and paying 1.8% total inc vat is closer to the average. In a lot of cases that is not far off from what is paid in the US. Another big difference is the US has the MLS, with virtually every home listed, and the UK has multiple marketplaces and not everyone will see every home. To reach almost everyone you need to use multiple agents and pay a higher fee, if you use a sole agent, you are not reaching all registered buyers. This is more of a problem in a buyers market, if you have a home in a hot market you will find a buyer either way. Multiple agency is not needed in the US.
As a point of reference in the UK it's around 1% commission to sell your house, they do the marketing, including on a variety of websites.