The most significant investment most people make is their home. That makes buying and selling a home one of the most critical transactions in which a person or a family is involved. It involves:

a) laws and regulations (federal, state, and local);
b) financial knowledge;
c) dealing with more significant figures than usual.

On the part of the sellers, there are also many emotions at play. For example, people usually value the history of their house and the memories it contains, which will constitute a problem in the sales price negotiation.
Real Estate transactions involve dozens of decisions and substantial time, energy, and money investments.
The objective is to find a buyer that values the house and buys it at the highest possible price. For that, you need a solid presentation and a solid  marketing plan that makes the buyer fall in love with that house and choose it from all the other options in that market.
A seller needs to know his home’s market value, best listing price, negotiation tactics, and improvements that offer the best return on investment (ROI). A seller might master all these matters and sell the house by himself or be better advised and get a Realtor. In general, we see that houses sold by Realtors achieve better prices than houses sold by owners.