For people in the age group that commonly does this, they know which part of the sentence the interjection is likely to appear in, and their brain can automatic

For people in the age group that commonly does this, they know which part of the sentence the interjection is likely to appear in, and their brain can automatically filter it out, so it doesn't bother them and they don't even see it as a problem. This applies to all verbal interjection. You use some form of verbal interjection too, but of course you don't even notice that you are doing it, and you would also get angry if some other people told you that your speech pattern is stupid and that you should change how you naturally speak.