People of other religions receive religious education, and therefore, have faith in and propagate their religion.
Conversely, Hindus lack education on Dharma, and hence, lack faith in Dharma.
They also develop doubts about their Dharma, because of the so-called rationalists. Therefore, they not only avoid propagating Dharma, but some of them also undergo religious conversion.
Whatever little propagation of Dharma takes place is only because of Saints and spiritually evolved individuals.
Some Hindus do have faith in Hindu Dharma because they get spiritual experiences by being in the company of Saints and the spiritually evolved.