Because 90% of people can't read IPA... I mean really? Does ˈθʌndərəs mean anything to anyone looking at it?
Highlighting specific syllables and spelling them a way that you can only pronounce one way is a lot more logical imo...
@Aboves a few posts, Rakou is one I have heard about 10 different variants of... But nothing beats Chimmy-Choo for Chimecho.
I'm on a mission to train every Pokemon Family during a playthrough of 3rd to 5th Gen! Currently at: 532/602!
Current Team (White 2 [4 badges]): Vulpix/Zoroark/Mr Mime/Cherrim/Deerling/Marshtomp
Current Team (Black 2): Solrock/Emboar/Sunflora/Crobat/Dunsparce/Azumarill