there's a difference between uttering a prophetic word for the church via tongues than just praying in the Spirit. tongues also edifies us as individuals. so if a person is just off to themselves in the church caught up in worship and they're praying in tongues to God, then they are edifying themselves and not the church as a whole. in that situation there'd be no need for interpretation, because the word is for that individaul and not for the church as a whole. that's why the Bible says he who speaketh in an unknown tongue speaketh unto God.
when a person has just received this gift, they dont know as many words as those who have had this gift longer. gifts are built upon as they are exercised. that's with any gift. so its the same way with tongues. i was baptised in the Spirit a little over a year ago, and when i go to church i'm surrounded by more seasoned saints that have been speaking in tongues half they're lives, so they know way more words than i do. and also, tongues is an entirely different language from English. in English one word may have just one meaning, but in other languages sometimes a word may express a phrase or several thoughts, but the Spirit knows the interpretation. so it may sound like to us they are repeating the same words, but we dont know what the Spirit could be expressing throught that individual. and not all tongues are the same language either, so we really dont know what's being said unless God has graced us with the gift of interpretation of tongues, which is a whole other gift all by itself. so these are all things that we have to take into consideration with this gift.
another thing that should be considered is the order of the house. not all churches have the same rules regarding the exercising of spiritual gifts. some allow more room for the Spirit, and some are very strict. like some churches may let a prophet prophesy to people individually in public and to the congregation as a whole. but then other churches only allow individual prophesying in private. so the order and the structure of the house has to be looked at too. so there's a lot to take into consideration when it comes to spiritual gifts.