The current GST model is designed to levy CGST and SGST across the entire goods and services supply chain i.e Manufacturing → Wholesaler→ Retailer→ End Consumer.
The Government (Central and State) exercises effective control on the first three stages of the supply chain. But does not enjoy same command over the last stage where supply is made to unregistered supplier i.e. Consumer.
Hence, in certain cases small retailers can sell goods without GST bills and escape tax for sometime. But in the long run, there is also a probability of the Government cracking down on culpable retailers.