Why MLC_ENABLE_SENTENCEPIECE_TOKENIZER OFF by default?

Should MLC_ENABLE_SENTENCEPIECE_TOKENIZER be on by default in CMakeLists.txt? I had to turn it on in order to successfully run ./build_and_run.sh to build the example target. Otherwise, I get a assert failure at src/sentencepiece_tokenizer.cc:

#else
std::unique_ptr<Tokenizer> Tokenizer::FromBlobSentencePiece(const std::string& model_blob) {
  assert(false);
  throw;
}
#endif  // MLC_ENABLE_SENTENCEPIECE_TOKENIZER

Start in CMakeLists.txt and inspect the default for MLC_ENABLE_SENTENCEPIECE_TOKENIZER, then trace the disabled path in src/sentencepiece_tokenizer.cc. Run ./build_and_run.sh with the current default and with the option enabled; done means the intended example target builds and runs without a manual configuration change, or the required configuration is clearly established.