@Bijay
2 simple answers and I can state this as a matter of factly, having talked about this at length wth some very senior ppl in Symantec who are concerned with SEP and Licensing.
1. Looking at the Licensing systems for SAV 10.x, which needed the license file for even huge corporate setups and with increasing complaints from admins for SAV that it becomes difficult to track / maintain licenses in an infra that has several thousand computers changing day in and out, it was decided that Symantec do away with the licensing mechanism for SEP. It's a paper licensing based format, which is better to maintain, and can be rectified with some simple steps in case the admins find that they are exceeding the number of licenses. Something akin to Microsoft's VLK's.
2. The licensing Infrastructure and complexity of the systems required to do the same for SEP 11.x, is too great w.r.t. maintainance and more. hence the need to perform licensing only for SEP SBE.
HTH