I appreciate the question.
The working income tax benefit will be enhanced beginning in 2019, meaning that the maximum benefit will increase, both for single individuals and families. In addition, an inclusion rate will be applied to the enhanced benefit so that low-income workers can access the maximum benefit more quickly. The rate will be lowered so that people can qualify for the benefit across a wider income range.
In short, the purpose is to roughly offset the additional contributions made by low-income workers during their working lives.