Industry connections can be a great thing for a non-technical co-founder. If you know have relationships with the top widget users in the world then it would be a huge boon to your widget-related startup.

Other qualities non-technical co-founders can bring: money, social/sales/pitch skills, outsider opinions (from not having possible preconceived notions of generally accepted technical limitations), industry experience or experience in general.

Also, I hope it is clear I'm not saying technical co-founders can't bring any/all of the above.