Someone tell me why the Congress writes letters rather than issue subpoenas.
I know the process can be frustrating but the step by step rules must be followed for the final results to achieved. Try to think of a baseball game where the batter comes up to the plate and on the first pitch, hits the ball over the center field fence. Before he and his team are credited with a score, he must first run the bases, touching all four in sequence. If he misses a base or decides to simply return directly to the dugout, no score. The legal system is rule based, as is much in our everyday life, and if you don't follow the rules, you don't get the desired results.
Senator Grassley is an old farmer. He is well aware that you don't harvest your crop until it is ready. He is also very tenacious.