My experience has been that PDX security is better than average. In the past I have had very thorough security checks there (once they took about 40 swabs for explosives, but they did ask me first, and it was a training exercise which I chose to co-operate with as I had interesting baggage, enough time to flight departure, and faith that I would pass the tests). The same security checkpoint that you have trouble with has also made a point of keeping my baggage in sight while being searched ... so it does seem to vary at times. As my experience with the same checkpoint is so different from yours (and my impression is that it would rank in the top 5% of airport security checkpoints, while you would pick the bottom 5%), I can only conclude that the problem is not systemic and was specific to your experience. The lesson, if any, is that security is random and has lots of room for improvement (in a systemic way). From your description it sounds like I've been through more security checkpoints than you (not that it represents a significant sample size, or makes my experience any more representative).
But I do have to point out that PDX security has it's good days and even shines some of the time.