It is not good to consistently give a short talk after every Prayer because first, people may feel bored, and second, some people may think that it is an integral part of the salah itself.
Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states: It is not a good idea to give a short talk after every Prayer without giving people a break; for in this way people may be conditioned to think that it is integral part of salah.
Indeed, this has happened in some communities in similar cases. For example, the collective du`aa’ which some imams are in the habit of making after each and every salah, even though it was not done by the Prophet (peace and blessings be upon him) or by the early Muslims, nor was it prescribed in any of the four schools. It was introduced with a good intention in countries where people were new to Islam; thus, they thought it would be hard on them to learn and memorize du`aa’; so in order to facilitate their learning of transmitted du`aa’s the practice of collective du`aa’s after every salah was introduced. Unfortunately, as people have become used to it, they are often under the impression that it is integral part of salah; so many of them now seem to think that salah is incomplete without collective du`aa’; thus, they ended up distorting the salah that was transmitted by the Prophet (peace and blessings be upon him).
Therefore, it is advisable for imams to avoid establishing the practice of giving a short talk after every salah. However, there is nothing wrong if this is done occasionally. Let us never forget the Prophet’s saying (peace and blessings be upon him), “Pray as you have seen me praying.”