They allow the business to compare performance between departments / across products / brands etc

This allows the business to make decisions about underperforming areas

If a profit centre is identified as doing well businesses may want to focus on the reasons behind this

They allow a more focused study of a firms finances

Benchmarking can take place

Responsibility for a profit / cost centre will motivate the individual responsible

By placing responsibility with the person involved in the activity the finances may be run more efficiently than would be the case if a more remote, senior manager controlled it.