The Hindu Marriage Act is appropriately named even though it applies to other religions like Sikhism, Jainism, and Buddhism because: (1) these religions originated from Hinduism and have similar practices, (2) proponents for separate personal laws have not shown that their laws are entirely different from Hindu laws, and (3) having diverse laws based on religion could breed resentment among people.

1. HINDU MARRIAGE ACT, 1955
FAMILY LAW ASSIGNMENT
The religious practices of the Sikhs, Jains and Buddhists vary from those of the Hindus but in my opinion it
is completely fine naming it Hindu marriage act as:
Buddhism, Jainism and Sikhism have originated from Hinduism.
People demanding separate personal laws should initially identify if their personal laws are entirely
different from those of the Hindus.
Diversifying laws with regard to religions will inculcate grudges amongst the people
however, they have no codified jurisprudence except that they were derived from Brahmanical sources
like Dharmasutras, Smritis and Nibandhs.