Considering that digitalRead() can only return HIGH or LOW, if the value is not HIGH, is there any possible way that the value can be anything other than LOW?
If you come to the correct conclusion that there is not, then explain why you need to test for HIGH.
The if/else if(/else) construct is used to test multiple conditions when there could be more than two. The if/else construct is preferred when there are only 2 possible conditions (as in the case of digitalRead).