I came across many bugs and the top resons for not fixing the bugs, even when they are valid are as follows:
1) Native OS doesn't support it.
2) As we dont claim we are RFC XYZ compliant, so we won't fix this issue.
3) This bug doesnt affect the functionality in any way.
4) As this is very corner case and not observed in common scenarios.
5) This issue seems to be related to third party software not to our codebase.
6) This bug does not affect the performance of the device.
7) Workaround is available so issue is resolved.
8) This is not recommended setting so wont fix it.
9) Hiding the configuration paramters . If issue is in paramters hide them and fix it.
Please add your comments , i'll be happy to know what other common reasons you come across for not fixing the bugs...