For a big corporate such as Safaricom, custom fonts is crucial, especially on the logo. That is why you see even Airtel has an entire alphabet of custom fonts. Most of these big companies do. I can see Equity Bank and KCB too nearly have the whole entire alphabet comprising of custom fonts (Especially KCB). Don't forget Telkom too, their logo comprises of custom fonts.
For the logo, at least, fonts have to be custom.