Many Kenyan businesses run entirely on WhatsApp and social media, and for some that genuinely works. The question is not whether social media is valuable, but whether it is enough on its own.
A website matters most when customers research before buying, when you sell to other businesses or institutions that expect a verifiable presence, when you need to explain a service in more detail than a caption allows, or when you want enquiries to arrive in a structured, trackable way.
It matters less if your entire customer base finds you through physical location and word of mouth, and you have no plans to sell beyond that radius.
If you do decide to build, start smaller than you think. A focused site that clearly explains what you do, who it is for, and how to get in touch will outperform a large site with vague content.