That's not true.
First, though, focus groups are not used to select the songs to play. Perhaps the lack of understanding of how music is really tested is why you think research is bad.
Auditorium Music Tests were developed in the 70's to replace the no-longer viable singles sales and jukebox data. When Top 40 was pretty much the only option for the under-40 group, singles sales were a good indicator. But when formats fragmented and singles were being phased out, record sales no longer could be attributed to one specific station.