Too often, Christians don't want to work to synthesize or harmonize Scripture, but are content to leave it in tension with itself, choosing instead to preserve their favorite notions about God's Truth even if doing so requires constant eisegesis or an outright denial of certain parts of the Bible.
It's actually not that difficult to reconcile the statements of Paul and James - so long as one has a good grasp of both the immediate and larger, whole-Bible contexts of their writings. What I so often encounter, though, is one believer who has invested significantly in what is essentially a works-based conception of salvation, and another who is committed to salvation by grace through faith, who simply lob apparently contrary verses at each other, neither believer developing a good synthesis of Paul's and James' words that comports well with the whole of God's word.
It's not that the truth is not there, plain and straightforward in its presentation (for the most part), but that the readers of God's truth have their own agenda, their own personal preferences, and are very often ill-equipped to properly suss out what God's word is actually saying, putting it all together into a cohesive whole.
When I was a child, it was common for seminary-level, systematic theology to be taught in the Adults' Sunday School class. In these classes, believers were taught not only what the doctrines of the Bible were, but how to study God's word and properly interpret its contents. It's been over three decades since I've seen anything like this in any church I've attended. The absence of such teaching has really begun to show: profound, widespread spiritual juvenility overtaking the Church and prompting (among other things) the view that Scripture is an impenetrable collection of contradictory, archaic and thus largely useless religious ideas.