Thank you for asking these questions and helping me grow in patience and understanding. I go back to my point that God saw it fit, the gift of tongues, to place it amongst the nine gifts of the Spirit. If God saw the gift as a necessity to edify both the believer and fellow brethren who are we to disagree because we lack understanding? You ought to at least acknowledge that truth. God saw it fit to equip His saints with this gift thereby qualifying it as useful and beneficial.
Whether I or you can understand or explain its benefits does not negate the fact that God has seen it as beneficial and has equipped His children with it. I just want to make that clear. Our ignorance does not supersede God's providence, and wisdom in distributing the gift of tongues and interpretation for the edification of both oneself and others.
Now, I can attempt to explain the benefits, as I have, but it doesn't seem to me you're all too interested in the benefits as you are disqualifying the gift. If I am wrong on that, forgive me. Lets say that the benefits of tongues can simply be equaled in regular prayer. So what? Then let me pray in tongues ("forbid not to speak with tongues") and let you speak in your native tongue. You have no right, or foundation in scripture to tell me to stop or that I am out of line to be operating in a gift the Lord has granted. The fact that He has granted it reveals its usefulness, in fact it qualifies it (regardless of our ignorance to its edification).
So this isn't a matter of agreeing to disagree. This is a matter of letting me walk as scripture gives me the right to and for you to do as well. If you have no desire to speak in tongues, then don't. I do, and have been equipped to do such. Lets be in unity within the liberty we share.