Might that impression be caused by Ostrava's arena that's smaller? Or are people at Ostrava madder about tennis? Anyway, I just read from TF that all tickets for Fed Cup final in Prague were sold in Monday when the sales started. So interest seems to be huge. Hopefully the atmosphere is great in both finals.
TF doesn't count. Ostrava is a better sporting crowd than they are in Prague, that's where the Czechs have their best fans.