That's not quite true. Asian countries have used mobile phone data in some cases but so have western countries.

South Korea got somewhat lucky (so far) due to the weird way it got into the country, via a cult that was already in effect socially distancing themselves and that was filled with young people. But now their cases seem to be growing again.

Also what do you think happens to mobile phone tracking the moment someone walks into a subway system? Orwellian surveillance isn't a magical panacea.