It is not a legal requirement to use an agent to sell your property – you may elect to undertake the process yourself.
However, there are many reasons why people generally engage the services of a professional to ensure the best price.
Aside from the obvious expertise in marketing, negotiation and selling that an agent brings, most buyers also prefer not to deal directly with the seller. If buyers know you are not paying for an agent, they will usually expect to see the house price reduced accordingly.
In the end, selling a property on your own might lead to a lot of work and pressure, without actually saving any money or maximising the end sale value.