Oiling the gears is often not necessary in some services, but sometimes people are shy and will not allow God to use them in a service unless they are “nudged” into action. I have seen this be remedied by a tongue and an interpretation in a service. Thank God for the “oil of the Holy Spirit”.
The question is if a person does seek understanding of a certain scripture and has been saved many years, why has he still not been given the revelation or clarification he has been waiting for? I can’t know why or when the truth will come to this person. If it is a matter of waiting to hear from God through a manifestation of the Spirit, this person may need to attend a church that allows manifestations of the Holy Spirit. But God can speak to anyone in whatever way that person believes that He can. So he should never give up his asking to understand the scripture better.
Where does it say that tongues is a public message? I see tongues as always prayer to God that is overheard by others. Interpretation is therefore also prayer to God. When people in the congregation hear both, they know what their prayers should be like. They are blessed and inspired to pray according to God’s will.