"c" for "ts" has a very long history in Latin script - pretty much all Slavic languages and many other Eastern European languages that use Latin use it in this manner, as does German in many cases. That's why it also has this meaning in Esperanto.

I do agree that the currently dominant English convention of adopting spelling from other languages (or their standard Romanization system) as is - or worse yet, dropping all the diacritics but keeping everything else as is - is misguided. But it doesn't help that English spelling can get very unwieldy when trying to spell something phonetically, especially across many dialects of English due to considerable variability in how things are pronounced. This has also caused problems - for an example of that, look at the still-common Korean Romanization of names such as "Park" which does not accurately represent the actual pronunciation if you pronounce it as an American would ("r" is silent - it reflects the non-rhotic British pronunciation, and was put there because the more straightforward "Pak" would tend to be pronounced incorrectly by a Brit).