I know that it is better to use rem (or em) unit instead of px, in order to keep text style scale when changing the browser's font size option.
So I only use relative unit in my projects instead of px.
But on mobile my thought is that it's not possible to change browser font size in mobile, unless there are accessiblity buttons such as 'A+' 'A-.
So I was wondering if there are any other reasons of preferring relative units instead of px in the case of mobile only ?