You control it
You need to keep in mind that social media is just like a lease, you use it, but it is not yours. You do not set the rules, you cannot make changes on how it works, and it can be taken away from you at any time. Otherwise, by having your own website you can set your rules, you are the one who decides how to manage it and the type of content you want to share, and it allows you to create the image you want your potential clients to perceive from you.
Brings credibility to your brand or business
Having a strong social media image is great, but having your own website allows your customers and potential clients to get the whole picture about your brand. When someone visits your website, they can go through every detail you allow them to know, and this can really differentiate your services from your competition.