Should I add Hindi / regional language to my Magento store?

If > 30% of your traffic is from Tier-2/3 cities, yes. Magento supports it natively via store views + locale CSVs:

• Store views per language (en_IN default + hi_IN + ta_IN + te_IN as needed)
• Translation pipeline via Crowdin / Phrase, auto-pulled into per-store-view CSVs
• Hreflang tags wire correctly (en-IN vs hi-IN) so Google serves the right page
• Indian customer-data: Aadhaar mask, PAN format, 2-line address (House + PO/landmark)

Top languages by GMV impact: Hindi (national reach), Tamil (Chennai/TN), Telugu (Hyderabad/AP), Marathi (Mumbai/Pune), Bengali (Kolkata/WB).