The problem is that people bring this into the church, against the instructions of the same Paul they use to justify their "unknown tongues".
For those who insist on speaking tongues in the church, their "gifts" of speaking in tongues should first be verified by interpreters. There are so many charlatans and deceived who believe their babbling or jibberish is speaking in tongues, that it drowns out any who really can speak in tongues (if these people even exist anymore).
1 Corinthians 14:9 - 13
9 So likewise ye, except ye utter by the tongue words easy to be understood, how shall it be known what is spoken? for ye shall speak into the air.
10 There are, it may be, so many kinds of voices in the world, and none of them is without signification.
11 Therefore if I know not the meaning of the voice, I shall be unto him that speaketh a barbarian, and he that speaketh shall be a barbarian unto me.
12 Even so ye, forasmuch as ye are zealous of spiritual gifts, seek that ye may excel to the edifying of the church.
13 Wherefore let him that speaketh in an unknown tongue pray that he may interpret.
Paul preaches against doing this in the church, even if the "unknown" nature of the tongue is the argument for the validity of said tongue.