Why do I pay gst and hst on goods for my personal use that were purchased and paid for in India ?

When you are importing to Canada:

1. for a personal goods you have to pay duty (if applicable) and HST (according the province), for example: for ON-13%. for AB-5%.

2. if you bring for commercial purpose (under your Business name & #) you have to pay duty (if so) and GST 5% only (and you can claim it back later, at the end of the fiscal year).