The Lord often requires that we call for help and ask others to pray with us. He says you're to ask, and then you'll receive. (Mat.7:7) "Is there any sick among you? Let him call for the elders of the church and let them pray over him." (Jam.5:14) It's important that you make your request known, not only to the Lord but also to your brothers and sisters.
If the Lord knows your needs before you call (Mat.6:8), why doesn't He just go ahead and supply them without your having to ask? It's mostly for your own benefit. Similarly, you can pray for yourself, but then there won't be as great a testimony. When you ask others for prayer it's not only a manifestation of your faith in Him, but also a confession of your need and your dependence on the Lord, as well as a greater testimony to all when the Lord answers!
He likes for you to ask publicly for prayer so that everybody can join with you in prayer, and everyone will then be manifesting or confessing their dependence upon Him and manifesting their faith along with yours, so that when He answers, it will be a general testimony to all of you that the Lord is the One Who heard you and answered prayer! Amen?--ask!