Is binary logs required on the slave in order to do replication?
Other than doing point-in-time restores, there are two additional reasons a Slave could have binary logging enabled.
REASON #1
If a Slave is also a Master

binary logging must be enabled on Slave
log-slave-updates must be enabled on the Slave

This would allow another Slave to connect to a Slave with binary logging enabled as a Master
REASON #2
If a Slave is not a Master, but you want to failover to the Slave to become a new Master

binary logging must be enabled on Slave
log-slave-updates must not be enabled on the Slave (this prevents binary logs from growing on a Slave as long as the DB Server has the role of a Slave)

That way, after failing over your application to the Slave to become the Master, you do not have to restart mysql to enable it later. You could then setup replication to the new Master.