I am a muslim and follower Islam not by chance but by choice. Islam is not just a religion its a way of life. People must know that THE QURAN is the most rational scripture (source of which is God) and it invites people of reason to reflect on its content and reflect about the universe. It says its a word of God and invite mankind if any one disagrees with the claim do the following to disprove it. Scientific community call it as theory of falsification... Islam is truth and should be proclaimed and is also open towards criticism with proof.
There are times when it can be appropriate to convey your religious perspective. This can help people understand what motivates you and your actions. Sometimes it's good to express what values you uphold and perhaps even rally like-minded individuals to your cause. Particularly if you are doing something positive, it can inspire others to see the merits to you faith.
I can see the logic behind religious behavior. Obviously they believe their religion is very important to their life and well being in this world and the next. Without religion, they would have no reason to believe that their life exists beyond their death and, to them, would make their lives pointless. They also tend to feel that their religion is truth and that others should be told this truth.
Holding a religion is rational, because the dictionary definition of religion is (quoted directly from dictionary.Com) "a set of beliefs concerning the cause, nature, and purpose of the universe, especially when considered as the creation of a superhuman agency or agencies, usually involving devotional and ritual observances, and often containing a moral code governing the conduct of human affairs." Holding a religion shows that you believe the truth of a greater being (or beings) that exists, it shows that you wish to conduct yourself with a higher standard of morality than the world around you, it shows that you wonder about the workings of the world and the universe. Sharing your beliefs publicly is rational, as well, because when your life has been greatly altered for the better, it should be shared with the general public so that they may follow the path that you took and have their own lives improved.
Off the top of my head a very simple reason to rationally hold a religion is because it helps define whom you are as a person, this is similar to declaring a political party. As to a rational example to proclaim a religion would be dating. Again it assists in helping to explain whom a person is and how they think.
Ps I hope I interrupted the question as was intended.
If one is holding and proclaiming for the purpose of gain or a greater cause than yes, there are some. Most hold their faith irrationally, but the occasional outlier could reason out why they would do such a thing. I disagree with most of the other Yes's reasoning, but that wasn't what the question was about.
There are religions out there, namely the Christian religion (according to its own scriptures, the Bible) that require believers not only to profess their faith publicly, but to attempt to evangelize others.
If a religion requires its followers to profess that they are a follower of that religion, then it should be done by those individuals to maintain consistency.
Matthew 28:16-20 states:
Then the eleven disciples went to Galilee, to the mountain where Jesus had told them to go. When they saw him, they worshiped him; but some doubted. Then Jesus came to them and said, “All authority in heaven and on earth has been given to me. Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age.”
Religion itself is irrational, a set of beliefs based in faith, not reason or logic. Holding a religion only shows that you hold beliefs that are irrational and unsupported by evidence. And as far as professing your belief, that's well and fine, and normal human behavior. However, the only way it can be rational is because believers feel it is the truth, and it's rational, in general circumstances, to tell others what you feel to be true.
I do not think it is necessary to profess your religious beliefs in public. Due to the nature of morality and the vague core of religions and dogmas in general for philosophy it is impossible to convey with any level of clarity what you believe in entirety including the nuances, all of which matter to the listener, of your own beliefs.
People should by now realize that all religions are just Superstitions and nothing more. They can have an interest in them, sort of take your pick as to which one you will have an interest in today, but, essentially they all have the same elements as other Superstitions like Astrology. What will I follow today? Christianity, Islam, Astrology, maybe I'll just have my palm read today instead.