You have noticed that on many client machines the Software Management (SWM) plugin is not being updated after you upgraded from ITMS 8.7.2 to ITMS 8.7.3 version.
From Symantec Management Agent (SMA) UI, it seems like the reason is:
Skipped after detection check
Like detection is not able to either find active version or does not match the upgrade version.
ITMS 8.7.2, 8.7.3
Known issue. Plugin install/uninstall/upgrade rules were updated to check registry content (same way as basic inventory).
Affected solutions: Patch, DS, SWM, Monitor, Inventory.
This issue has been fixed with our ITMS 8.8 Release.
For those with ITMS 8.7.3 release, refer to the pointfix available at: CUMULATIVE POST ITMS 8.7.3 POINT FIXES: