Each email client and platform supports their own set of fonts.
Due to that, assigning a font to your signature which a platform fails to support will cause it to assign a different font altogether.
Sometimes, the default font set by the platform may be so different in style as to break the signature’s design.

Rather than assigning a specific font, which may be missing for some platforms, Signite elected to use font families, which causes the platforms to choose a default font with similar characteristics to the one your browser uses, if the exact one is missing.
This method mitigates the issue and keeps Signite’s signature legible and visually cohesive in as many platforms and email clients as possible.