what is the purpose of discussing hardy weinberg eq when the conditions are never met?

Hardy-Weinberg, as well as all other statistics operates on a set of assumptions which may or may not be met.  However, just because the assumptions are not met, does not mean that the statistical test is useless.  It simply means that we need to be aware of the limitations of the test (and potentially look for a more suitable test) and how those unmet assumptions may reduce the effectiveness of the test.  The Hardy-Weingberg equation is very accurate when all the assumptions are true.  When some of the assumptions are not met, the equation is still informative; simply less accurate.