st.markdown renders according to Github Flavoreded Markdown GFM. Although table striping is not part of the GFM-specifications, Github styles tables with striping. Streamlit does not.
I would appreciate to see Streamlit render tables with striping, too.
Row 2 of the following markdown string will be highlighted with gray background on Github, but not with st.markdown
| foo | bar | | --- | --- | | baz | bim | | highlight | highlight| | baz | bim |