Well, if all they taught was test taking methods, then sure, there's a problem. I don't have a problem with spending some time teaching students how to excel on standardized testing, though. I knew students that were great at homework, studying, work groups, and discussing the subject, but couldn't perform in a testing situation. In fact, some of the techniques to help people test well are simply time management effort focus techniques that can help them significantly down the road in work situations. Scanning the whole test and doing the problems you understand first, then hitting the problems that require some effort, then hitting those that you aren't sure how to approach makes a lot of sense when you're applying the same principles to deciding how to order your own work day.
That's not to say that a teacher should simply sit in a room, recite all the possible test questions and answers, and give a practice test every day.
I'm on the fence about teaching "why things work." There simply isn't enough time for a teacher to successfully teach the theory behind even 10% of the lessen material, nevermind all of it. There's a few levels of learning we have to be aware of:
Knowledge - Knowing some collection of information, and being able to recite it on command
Analysis - Applying knowledge to an existing "thing", understanding which knowledge applies to it, being able to apply that knowledge, and being able to define and understand the thing
Synthesis - Being able to understand a thing and the knowledge that applies to it well enough to change it, recreate it differently, or combine it or parts of it with some other thing to create a new thing
Dividing the subject up into portions of the lesson which will only teach knowledge vs portions where they'll teach analysis, vs portions where they'll teach synthesis is hard work. Defining a curriculum is not trivial. I think what people are concerned about is that once the tests were defined, teachers started changing the curriculum to address the tests.
I'm fine with that, as long as the tests represent what we want our kids to be learning. Does the test truly measure the analysis and synthesis capabilities of the student, or just the knowledge?
As long as the test defines what we want our kids to learn, then why wouldn't we want our teachers to "teach to the test"?
Is the problem that the tests aren't good at measuring true ability? Because if they are, then there should be no reason to complain.