Is your feature request related to a problem?

Every single time I have exported a dataframe (usually with .to_csv), I have not needed the index.

Describe the solution you'd like

Change the default from True to False.

API breaking implications

All code that has not explicitely set index=True should make it.

Describe alternatives you've considered

Leave things as they are now.

Not using the index is something usual or am I biased by my own experience?