I don’t think cowardice has anything whatsoever to do with this. For one possible answer with more credibility, let me quote from the great Bridgewater treatise by William Whewell (who was no evolutionist), written many years before Darwin (indeed, Darwin quoted it opposite the title page of the Origin).
“We are not to expect that physical investigation can enable us to conceive of the manner in which God acts upon the members of the universe. The question, ‘Canst thou by searching find out God?’ must silence the boastings of science as well as the repinings of adversity. Indeed, science shows us, far more clearly than the conceptions of every day reason, at what an immeasurable distance we are from any faculty of conceiving how the universe, material and moral, is the work of the Deity. But with regard to the material world, we can at least go so far as this;–we can perceive that events are brought about, not by insulated interpositions of divine power exerted in each particular case, but by the establishment of general laws.” (p. 356)
We must not overlook the influence of Whewell’s insight on many proponents of Evolutionary Creation, including me. Not to mention its influence on Darwin.