I think the reason why he does so is strategic. I know people hate to hear it, but GWB is not all that sharp. Hence, he leans extra heavily on the notion of the executive as someone who doesn't know jack about anything, but somehow has the ability to "make decisions" based on advice. How someone without expertise is supposed to process complicated advice is beyond me, but it's a strategy that enables GW, and those in similar situations, to take on leadership roles.
I can't really comment on the historical aspect of your post, because I just don't know that much about it. It's quite possible in the very early days, much was left up to Congress. Perhaps that's as it should be. I recall in the 1990s the term bandied about was "activist president", so perhaps even to this day there is this idea of the president as a magistrate only.
Finally, on the immigration issue, I think the president is basically doing what you are suggesting. His problem is that his poll numbers are very low. I think to the extent he's attempted, late in the game, to get out front of this issue, it's because he needs to politically, or thinks he does. He needs to appear to be engaged in the issue. But as with CFR, I fully expect him to sign absolutely ANYTHING that hits his desk, and so far, that's been the case 100% of the time.
Great to "hear" from you, though. Reminds me of the fun times we used to have, pre 9-11.
I read quite a few thread where the exchanges are way-too "food-fight" for my thoughts to contribute much.
I don't generally disagree with your observations in your first paragraph. However they don't negate the fact that he stated a wish for reform on this issue prior to his first election and immediately thereafter and then in the wake of 9/11 neither took action on the issue by execution in any forceful manner or by introducing a program.
Instead, he let it twist in the wind until it became a media "crisis" that he couldn't avoid.