Why are Computer Cabinets listed without smps?

Good number of low cost Cabinets will come with SMPS but we break them and make separate entries like "cabinet without smps" and "smps" so that the customer has a choice of picking cabinet of one brand and smps of another. This is significant since in good number of cases the default smps which comes with cabinet is not good enough. You can decide the quality and model of smps separately - you may select the default one also if you wish.
For example, you may select an iball cabinet and corsair smps for your computer.