Why all mates get surpressed?

Hello;

     I noticed sometimes when I go to an assy., I'll find that many of the mates are surpressed in it. Everything is left to float. I did uncheck suppress mates with new configuration. Anyway, I know there's probably different reasons for this to happen, but was just wondering what some of the causes are? It seems like it happens more then I would think it would.

Thanks, in advance for any input;

Rob_D SW2013 Sp3

SolidworksAssemblies