If a theory has a single hole, it is no longer a theory but an opinion, at best...or a dogma, at worst. The theory of Evolution is pseudoscience. Testable or not, what do we have here and today? We have a carpet with a lot of holes, so much that it is no longer a carpet. Why is it still believed, then? Easy:
A) There has been so much focus, thanks to a fanatical, uninformed World population to prove something that is flawed ("Evolution Theory") as opposed to look elsewhere for answers in regards to life, its processes and origins.
B) In the mind of the World population, the theory of Evolution has its own subtle tensions with the theory of Creation. That alone validates the theory - God, even as an idea, is a hated creature on Earth. Everyone wants to be God (as shown by the increased number of "liberation" and "freedom" movements which imply a sense of super-independence as far as each individual goes) to the extent that there is no room for the idea, or possibility, of God. The theory of Evolution is used satisfy the denying mind.
C) Psychologically and socially speaking, and I make this observation with the increasing materialism of the World: it is easier to believe something that is wrong (The Lie) that is functional...as opposed to something which is right (The Truth) but is practically useless. The theory of Evolution offers a lot of practicality in that in the minds of many it stops all questions about Creation, God, Origins, and man's destiny. The idea of God, on the other hand, is very detestable and is rather impractical - supposing that we are sincere enough with ourselves, we can then admit to ourselves that the ill-founded mind functions more sufficiently when an idea of a master or a watcher (i.e. "God") is erased or downplayed into nonexistence or triviality. Given the current state of the world, the distress that befalls almost every individual - however much they admit this or not - the state of loneliness, meaninglessness, the need to be beast-like, crude, and largly amoral is funded by the belief that there is no God, no meaning, therefore, "everything is possible." In other words, it gives the amoral, criminal, filthy mind its justification for doing what it does.
D) Supposing we take the leap into the belief that Evolution is essential and truthful. At that point, it is logically implied and proven that Man, as a species, had began at a very specific point in time, as a specific form, and evolved from that point. If the theory of Evolution is the truth, it would be even a greater proof of an intelligent designer as opposed to the random and seemingly spontaneous existence of Man. Therefore, in all cases, the theory of Evolution paves the path towards ID Theory, and not detracts from it. Which brings me to this point: the reason no one wants to accurately study and test the theory of Evolution is because if it is proven, IDT becomes that much more difficult to deny, and at that point, Man would have to lose his psychological comfort in knowing that there is a possibility of the inexistence of God...because...Man wants to be God, and thus hates the idea of an exterior, superior God. Hence, the theory of Evolution remains largely and for the most part as a "Theory" because otherwise, Man might have to give up his fantasy of being a God, at least on a psychological level.
However you argue with it, IDT becomes harder and harder to deny as scientists and laymen fumble around trying to find ways to disprove it...
Eventually the question ceases to be "Is there a God?" and becomes "Who is God?"