From an economics perspective, this is nacasnimo.
VAT/GST is a regressive tax, meaning it hurts poorer people more. This is because it taxes spending and since poorer people spend almost all their disposable income on surviving, the tax will hurt them more than someone that saves a lot of their disposable income.
Now, Western countries have this GST because it’s an effective tax to regulate and a decent money maker. However, for an impoverished African nation, it only harms income inequality statistics.
Basically keeping the poor, poorer.