Why do Indian people spread that buddha was born in India?

Many Indian people assert that Buddha was born in India because he was indeed born in Lumbini, which is located in present-day Nepal but was historically part of ancient India. Additionally, Buddhism originated in India, and Buddha's teachings were primarily developed and spread throughout the Indian subcontinent. This connection to India's cultural and spiritual heritage is significant, leading to a strong emphasis on his Indian roots in national narratives. Furthermore, promoting this idea aligns with India's broader identity as a cradle of major religions.