Intrusion Prevention and Browser Protection

I see that these are two different features in NIS 2011.

 

  1. Am I correct in thinking that although Browser Protection is limited to IE and Firefox, Intrusion Prevention applies generally whatever Browser is is use?
  2. However the purpose of these features appears to be fairly similar - so what is the real difference?
  3. Also it seems odd that vulnerabilities applying to particular 3rd party software products aren't generally getting patched by their own manufacturers?