Why no .dict file is generated

I am following the quick start in:
python preprocess.py -train_src data/src-train.txt -train_tgt data/tgt-train.txt -valid_src data/src-val.txt -valid_tgt data/tgt-val.txt -save_data data/demo

I got the following 3 files:
demo.train.pt
demo.valid.pt
demo.vocab.pt.
I could not get the following 2 files as mentioned

demo.src.dict
demo.tgt.dict

I trained 2million fr-en sentece pairs, everything went smooth, but the translation result looks very bad, even the sentence in the training source file are not translated correclty and report unknown words. Any suggestion? I follow the quick start step by step.
Thank!

This is the quick start tutorial I am following, using all the default parameter.
http://opennmt.net/OpenNMT-py/quickstart/

Thanks!