>>53372751If I had to guess, they can't be asses with the job of taking out the audio for both the voices and the music, while retaining Bayleef, who in her return episodes, has been making noises along side other Pokemon/when Ash is talking.
4Kids would sometimes lose Pikachu's voice and have no choice but to record new noises for him in the very early episodes, but later ones would just take audio of Pikachu from other episodes. I'd imagine it was a pain to find the right cry, but they did it anyway.
TPCi are not that dedicated, so they get rid of the original audio entirely.
The other option is they hate the viewers and know that the changes annoy them, but this isn't likely (or maybe it is, who knows)