Why don't you use the fonts used in a logo throughout the rest of the branding?
Hierarchy. Exclusivity. Just to name a couple reasons.
We want to ensure that your logo is at the top of the hierarchy. It is the part of your brand that is given space to breathe and is easily identifiable across all platforms. Using the fonts from your logo in a headline or a pull quote that sits next to your logo, the focus is pulled away, so designs become unbalanced. Rules are made to be twisted though, so we never tie the hands of our designer.
The font/s we use are custom typefaces (crafted by us), so the usability of this typeface as a font is limited. It will not look like the logo font as it's customised to the logo.
We choose supporting fonts that give the brand personality. Giving us multiple tools to take your brand even more powerful.