snakemake covering old output file

Question

I used 'snakemake' to build up a pipeline and run it, got some output files, and when I run the pipeline in the second time, it will restart from the very beginning step and even there has the output file of the step, it still runs it from the very beginning and covers the old file.

here is the command line:

snakemake --snakefile {snakefile} --jobs {jobs} --rerun-incomplete --nolock  --use-conda  --conda-prefix {conda_prefix} {add_args} {args}

is anyone knows what happened??

thanks