There could be a number of reasons for that. I might not have paid close enough attention other times when reading Isaiah 33. I may have been more attuned to a verse with such comfort since I had just learned of a tragedy in the life of friends. It may be that in previously reading a different translation I might not have noticed one of the striking features of this verse - "Be our arm every morning." (Although, I've read through the Bible in this translation before.) Some translations read "strength" in place of "arm." That's a legitimate translation, but the literal translation is more evocative than the generic concept it conveys. When you read arm, it calls to mind other places in Scripture the same word is used in displaying the saving, protecting, creating power of God.
Psalm 98:1 “Oh sing to the LORD a new song, for he has done marvelous things! His right hand and his holy arm have worked salvation for him.”
Isaiah 40:11 "He will tend his flock like a shepherd; he will gather the lambs in his arms; he will carry them in his bosom, and gently lead those that are with young."
Jeremiah 32:17 “Ah, Lord GOD! It is you who has made the heavens and the earth by your great power and by your outstretched arm! Nothing is too hard for you.”
That is the arm that I need every morning. "Lord, gather me in your arms this day. Lord, protect me from the attacks of the evil one today. Lord, be my deliverance today. Lord, carry me today because I can't get through it. Lord, save me today." And without the practice of daily reading God's Word, I wouldn't have stumbled across this marvelous prayer asking God to be my arm every morning, my salvation in time of trouble.
It is safe to say that there are truths in God's word you haven't yet discovered, even if you've repeatedly read through the whole Bible. It is safe to say that even if you keep reading for the rest of your life you won't mine all the gems that are there. So keep reading. Keep digging. And may God give us eyes to see and hearts to receive the life-transforming truth that is contained in his Word for us.