Because evolutionary theory looks like bad science. I don't see much of a connection between the evolutionary theories that I'm aware of and the factual evidence. Either evolution happened gradually or in great leaps. The lack of fossil evidence contradicts the former, and the lack of a plausible mechanism contradicts the latter.
IDers simply postulate design as an explanation for apparent design. For example, what would be a more "scientific" explanation for the discovery of a spaceship on Jupiter, the existence of extra-terrestrial intelligence or random chance? Similarly, it seems to me that design is a better explanation of "irreducible complexity" and order in nature than random chance, particularly since we know through reason the existence of God. (The notion of "spontaneous order" seems nonsensical to me, as it seems to violate either the principle of sufficient reason or the principle of causality).
In essence, then, you're proposing ID as a strictly scientific approach to the problem, which is certainly a valid thing (though not a universal goal among those who get collected under the "ID" banner).
But if you're going to approach ID from a strictly scientific standpoint, then you've signed yourself up for providing more than just an inability to "see much of a connection." Rather, you've got to show the specifics of where the current theory is incorrect; and after that, you've got to provide the scientific basis for why design is a better explanation.
IDers simply postulate design as an explanation for apparent design.
Well yes -- but on what basis would you objectively demonstrate that? What criteria could separate between "designed" and "naturalistic" phenomena? It would be hard enough to overcome "science's" existing animosity to ID, even with those criteria. Without them, ID doesn't stand a chance.