“I command that after my [Pari]Nirvana, Bodhisattvas and Arhats appear in response-bodies in the Dharma-ending Age, and take various forms in order to rescue those in the cycle of rebirth.
They should either become Shramanas, white-robed laypeople, kings, ministers or officials, virgin youths or maidens, and so forth, even prostitutes, widows, profligates, thieves, butchers, or dealers in contraband, be confreres of these kinds of people, praise the Buddha Vehicle and cause them to enter Samadhi in body and mind.
But they should never say of themselves, ‘I am truly a Bodhisattva’; or ‘I am truly an Arhat,’ or let the Buddhas’ secret [esoteric] cause leak out by speaking casually to those who have not yet studied, other than at the end of their lives and then only to those who inherit the teaching. Otherwise, aren’t such people deluding and confusing beings and indulging in gross false claims?”
~ The Buddha (Shurangama Sutra)
Buddha is clever. He knows exactly how we think and react. Buddha not only provides good teaching to buddhists who are interested to learn. He also did not forget to remind bodhisattvas and arhats that if they really want to help us, they should not disclose their identities to us. I think as a sentient being, I would also prefer not to have anybody tell me he is a bodhisattva. It will just give me unnecessary wandering thoughts. Furthermore, the boddhisattva will not be able to use his power to help me to become enlightened (even Buddha also cannot do that). Buddha will tell me that I have to work hard myself to study and practice buddha’s teaching (esp. when I am new in buddhism and don’t know how many more remaining years I have…need to work extra hard).