If you supply non-food packaging as well then those customers may not recognise BRC, they may not have heard of it.
If you are pretty much 100% food packaging then in my experience you can safely drop it from a certification point of view. That said if you export then maybe some of your overseas customers may not have heard about BRC, although this is getting less and less as GFSI standards are adopted more globally.
Many companies keep their ISO systems in place, but just stop the external audit.
If you drop ISO certification you will also not need to spend the time and effort upgrading to ISO 9001: 2015.
You should know your markets and customers best.
Regards,
Simon