A business needs to get more than one GST number if,
A business entity is supplying goods & services from multiple States, then he/she mandatorily required to register under GST in different States.
Further, any business entity can get multiple GSTIN even if they are operating from a single State under multiple verticals to avoid accounting complexity between multiple businesses.
Illustration
XYZ Private Limited doing the business of selling merchandise and also doing the business of selling software from Bangalore only. Still, a company can apply for multiple GST numbers for their different business domain.
If you are supplying goods and services from one state to all over India. You do not need multiple GST Certificates.