As Mr. Gerald Weston pointed out in a sermon recently published by Living Church of God (LCG), Mr. Herbert W. Armstrong often started his holy day sermons by asking the question, "Why are we here?".
On a holy day, why are we here? Why do we assemble for holy day services?
We are here because Mr. Armstrong believed the Bible more than the Church.
The Church of God Seventh Day did not keep the holy days.
Mr. Armstrong knew Christ was the head of the Church of God. But he never assumed that the Church of God leadership correctly followed Jesus Christ. Christ leads the Church through the Bible, the Holy Spirit, and circumstances, but Church of God ministers and leaders do not always follow where Jesus Christ leads. Mr. Armstrong never assumed that the doctrines of the true Church of God were all correct. He never assumed that the Church had the right interpretation of scripture. If he saw something in the Bible different from what the Church taught, he believed the Bible, not the Church. He believed God and His word more than men, even the leadership and ministry of the true Church of God.
So when he saw that the Bible taught that we should keep the holy days, he believed God, not the Church.
That is why we are here.