You are right that speaking in Tongues does not affect one’s salvation. However, as Paul explained it in one of his letters, speaking in tongues edifices (or builds up) the speaker’s spirit. There are also a number of other benefits that go along with speaking in tongues.
Unfortunately, it appears odd to people when someone is speaking in tongues without interpretation in the church service. It is even worse when many people are speaking in tongues at the same time in church. Based on Paul’s instructions not to do this, but instead to prophesy in the church, I believe the Pentecostal church is wrong in doing this.
However, this behavior is not normally done to offend or exclude other people. Instead it is more likely the tongues speaker is just caught up emotionally and doing what they’ve always seen done in the church without thinking through the implications or the Biblical instructions on the subject.
Anyhow, if you are a Christian and you don’t speak in tongues, tongues is a gift open to all believers. To not claim it is a bit like refusing to take the ‘free gift with purchase’ that comes along with salvation. We make too much of this gift in the Pentecostal denomination, as the essential thing is the baptism of the Holy Spirit and not the sign gift that usually (but not always) comes with it.