I disagree whole heartedly with you on this. The book of Wisdom is by far the deepest book in the OT and I would even make the claim that the book of Wisdom is for the OT what the gospel of John is for the NT.
Wisdom may be wonderful, but it doesn't have any plausible authorship by a prophet. It's part of Jewish wisdom literature. Actually, so are a couple of the books in the actual OT. The judgement described in the Jewish Encyclopedia is not one that modern scholars would make. But I didn't mean by "inspired" the typical common-language sense of an inspirational book. I meant that it was written by an actual Inspired prophet, who was speaking for God. That's what the Jewish decision was trying to get at. Again, I think they got it at best only approximately, but if you accept the traditional attribution of the Hebrew OT, it's not a terrible distinction.
As far as I can tell, there was a combination of reasons for the Reformers:
* They used the Hebrew canon, for reasons I already mentioned. Hebrew copies in Qumran and other evidence for Hebrew isn't the issue, and much of it wouldn't have been available to them anyway. It wasn't part of the usual Hebrew Bible. Discussions of the actual history of the Jewish canon is interesting. It's by no means clear that it was post-Christian. I believe the concept of Jamnia is a 19th Cent idea. They would more likely have known Josephus' account of the closing of the canon under Ezra. Josephus is a strong indication of what the Hebrew canon was in Jesus' time.
* There were doubts from a few well-known early Christians.
* Some of the more questionable doctrines seemed to be based on D-C books. However I should note that this isn't deciding, since Calvin did expositions of the relevant D-C texts in the Institutes anyway.
* The lack of quotations from the D-C books in the NT (allusions are a different thing) didn't help, although of course not every book in the OT is quoted.
* Jesus typical term "the Law and the Prophets" is unlikely to include the D-C books, and the Reformers surely would have seen it as referring to the Hebrew OT.
All of these can be argued, and I have no beef with Catholics for using the larger canon. But I think there's enough reason that it was sensible for the Reformers to use the Hebrew canon, as they would have known it. Educated Protestants should know the D-C books anyway, for their insight into the background of NT times. But I wouldn't quote it as canonical when dealing with other Protestants.
Catholics and Protestants use the Bible differently. I think the differing canons actually fit their approach. Catholics take a broader view of the role of Scripture. Wisdom literature works just fine for them. They can also deal with a "stepped canon", i.e. a canon with books having various levels of centrality. This is certainly the Jewish tradition, where the Torah is clearly at a higher level than anything else, then the prophets (which includes the historical books), then the writings, and maybe the D-C books. The way Protestants tend to use the Bible makes this problematical. They want only the higher levels of authority, with authors who are viewed as having verified authority from God, e.g. Moses, David, and the prophets, and the Apostles in the NT.
As is well-known, some Protestants toyed with the idea of making at least some level of distinction in the NT as well, but that never caught on. It's probably good that it didn't. James is an important balance for some interpretations of Paul, and the Rev gives a valuable perspective, as long as we don't treat it as a codebook we can turn into a timeline.
Of course some of these identifications turn out to be a bit dubious, but I still think that in both Jewish and Christian tradition, the D-C books are less central than the Torah and the prophets. That Catholics and Protestants would draw the line differently is completely consistent with their differing views of Scripture.