If the court has no ability to sequester witnesses, why hold the hearing where witnesses need to be sequestered?

I had a hearing recently in one of the local justice courts in Delaware County, state of New York.

There were 3 witnesses testifying for the prosecution.

It was obvious that there was a need for the so-called sequestration of witnesses.

I asked the judge to sequester witnesses, he simply stated that witnesses need to go outside because there are no premises inside the courthouse (a new courthouse, recently built) to sequester witnesses.

Then, when the first witness testified and went back, I requested that he be separated from other witnesses, and the court could not do that, because there was nowhere to separate the witnesses.

A relative of the defendant went outside, saw the witness who just testified and the two witnesses who were about to testify talking, came back and reported it to me.

I reported it to the court.

The judge got frustrated and told me to go myself outside and make sure that the witnesses for the prosecution are not talking.

Of course, this is not a defense attorney's job to do that.

My question to the Delhi Town Court and to all other courts where sequestration of witnesses is not possible for lack of space or premises - if there are no premises to sequester witnesses, why hold hearings where such witnesses are supposed to testify?  Trials? 

Wouldn't such failure to sequester witnesses invalidate the resulting decisions of the court based on such testimony?