YOU DO NOT HAVE TO use a real estate agent. Legally you are not prohibited from NOT using one in the USA. But it's riskier not to, but sure, for simple real estate sales, it's quite possibly moot and unnecessary.

But the threshold for "simple" is far lower than you realize. Say you merely buy a plot of land. What if the land is land-locked - is there an easement for access? You probably didn't think of that first but a real estate agent will.

The reason why agents exist for ANYTHING is to save time, money and reduce risk due to lack of knowledge of the law, lack of knowledge of construction or lack of knowledge of financial matters. Humans have finite memory and skills - even if you have an IQ of 200. You can't know or learn everything. And you wouldn't have time even if you could. Enter the concept of "agency" - a proxy person or organization that represents your interests and has more knowledge and time that you do.

I'm guessing you are young and because you have plenty of time, you don't see the value of any type of "agent" relationship. I understand - when I was young I was the same way. And I was 100% wrong in thinking that way.

Today, I see enormous value in using "agents" for just about everything because I have plenty of money but little time and I KNOW what I do not know.

So I keep a lawyer on retainer now (an agent for legal issues) who helps with selecting lawyers for IP, business, real estate, family law, etc.)

I also use doctors (an agent for medical/health issues). I also use a tax lawyer/accountant (an agent for financial issues).

And often people will hire engineers and programmers as "agents" to accomplish things that people with money use as their agents to invest in companies of people who can make things work. These agents are called Angel Investors and VCs. And you as a technical person are an agent of creating technology value that ultimate "uses" the investor's money to best use despite the fact the investors know LITTLE about technology but see creating it as a good investment.

The reason such agents make more money on homes they own is pretty obvious:

1. They know all the details of maximizing selling price ranging from Staging to Negotiation techniques. They have practice at it. The 3% they take is necessary and reasonable because why the hell would they work for free. Would YOU work for free?

2. They have incentives to use every trick and skill because of their experience at the job - a real estate agent knows that Staging can raise the selling price by 10%-20% despite costing $5K-$20K - in many markets that is a trivial positive ROI (my ex wife is both a real estate agent and stager in the SF Bay Area, for instance).

EDIT:

So one thing agents do is handle HUMAN issues. My ex, for example, uses what we in B2B sales call "consultative selling" where you do NOT lead with taking customers out to see homes. Instead you spend time upfront and preselect only the homes that fit what the customer really values and what they can afford. Honestly I don't see a computer program duplicating that kind of thing any time soon. Certainly not in real estate and not in B2B sales. There is far too much nuance, psychology and hand-holding to ever expect a computer to duplicate - and it's all 100% "real time".

It's completely delusional to imagine Redfin achieving that any time in the next 100-200 years even with exponential improvements in technology (which are not going to happen as most people predict - my B2B is selling into semiconductor markets and we know what that's going to look like in 10-20 years because of "continuity").

Note also: Singularity and Transhumanism is not real nor based on any Science. It's a cult based on anti-scientific faith-based assumptions that are trivially proven to be untrue.