[CentOS] Why does 'mysql' user has /bin/bash shell?

Hello,

Default MySQL installation on CentOS sets /bin/bash as shell.
I'm on a user cleanup task where I want reduce unneeded privileges to users.

What is the "mysql" user shell for? (What will happen if I change it to 
/bin/false or whatever would disable it's shell?)

It's not only a matter of SSH (I'm aware I can AllowUsers in sshd_config 
for example).