First off, thank you for the question, I am answering here in a new post instead of in the one you asked in, since that one is two and a half years old at this point. Your comment is linked above and I have linked this article back in the original spot of your comment.
Secondly, what we believe is that Scripture has laid out the "mechanism" by which God purifies. We see it as "necessary" because it is truth - and we must put forth the truth of God. Nathan recently posted an article here with scriptural references for Purgatory (click here). For the Church to withhold truth simply because it doesn't fit with Protestant theology would not be honest nor beneficial to the sincere believer who is seeking the fullness of truth, which, of course, we believe can only be found in the Catholic Church. The fact that virtually all of Protestantism either ignores or flat out denies this truth is quite telling, would you not agree?
Again, I urge you to read Nathan's article and if you have further comments or questions, feel free to post here under this article (which will not be moderated until 4 weeks after posting).