Your Dockerfile ENTRYPOINT's dirty little secret.

Dockerfile

FROM ubuntu
# Works the same on Centos too if you want to try it. ;-)

# "Shell Form"
# Don't do this. it fails to accept arguments from the docker cli
ENTRYPOINT cat

# "Exec Form"
# This is what you want. Even if the "Shell Form" seems to work for you. (See the transcript below.)
ENTRYPOINT ["cat"]

# NOTE: According to https://docs.docker.com/reference/builder/#entrypoint
# "Only the last ENTRYPOINT instruction in the Dockerfile will have an effect."

run.sh

docker build -t myimage .
echo -ne 'asdf\n\nqwer\n\n' | docker run -i myimage -e

transcript.txt

## Shell Form output (the ENTRYPOINT does not receive the "-e" argument)
echo -ne 'asdf\n\nqwer\n\n' | docker run -i myimage -e
asdf

qwer


## Exec Form output (the ENTRYPOINT receives the "-e" argument)
echo -ne 'asdf\n\nqwer\n\n' | docker run -i myimage -e
asdf$
$
qwer$
$

## Rationale
~# echo -ne 'asdf\n\nqwer\n\n' | cat -e
asdf$
$
qwer$
$