Why Rhinoceros was played (per @theothr1):

"......okay, so, Rhinoceros was played to honor the passing of fan Philip Andrew Cassels...Phish paid tribute to Phil by opening the Deer Creek show with the song he was listening to before he took his own life (when they found him, the tape in his truck's radio was right where Rhinoceros ends) shortly before the band kicked off Fall Tour 1997...the band was fully aware that Phil’s brother, former Pharmer’s Almanac editor and HT contributor Kevin Cassels, was at Deer Creek that night so, it was played for Kevin for Phil...a bit maudlin? Perhaps but, i know for a fact that, having absolutely no idea whatsoever that the band was gonna do this, Kevin was deeply touched by this "silent" (and emotional) homage."

https://forum.phish.net/forum/permalink/1377153155