There are many of occasions such as in Mark 7:36, and many popular explanations. I believe it is also that so that these would reflect upon themselves, individually as to what they have seen. For if they publish these great works as they did in certain situations such as these, they are more of gossipers than preachers.
Nevertheless, despite their deafness towards the word of God, God's glory is spread, but no thanks to them. (Matthew 7:21)