I think this is probably because TTRPG is not a very popular - or even recognized by most people - game, either in Taiwan or China.
Apart from the small number of players, it is true that Chinese language players are more likely to translate foreign games to play them, and they are rarely published commercially because the market is so small. In fact, most Chinese language users playing DND, COC, PF and other famous and popular systems use "resources" translated by fellow Internet users (in other words, pirated copies or Pirates), they post translations on a number of forums out of interest and for free ).
There are, of course, players who are willing to create their own works, but they are usually published in other online communities (in Chinese, obviously not in English forums) or sold at "fan fairs".
(i try reply, but can't. I dont know why)