Short answer: Mostly no, but keep in mind there are dentists who recommend a root canal even when the justification is dubious.
Long answer: There are many different reasons teeth need root canals but the most common reason is that the tissues inside the nerve canals die (become necrotic). Typically this can happen due to trauma (your tooth was injured by a fall or even from the trauma of a dental drill during routine dental work), a deep cavity infected it, the tooth has severe gum disease which spread to the nerve tissues or the dentist sees signs the tooth is melting from the inside (a very rare event called “internal resorption”). Once a tooth’s nerve begins to die, there are often symptoms associated with it and this is commonly known as a “toothache”. Occasionally, there are no symptoms at all and the dentist simply finds an issue detected only in an x-ray. If any of these legitimate reasons are present, it is a good idea to have a root canal done. Some people have cited health reasons to NOT have a root canal done even when one is justified (like severe pain). They believe root canals can poison your body or leave some infected tissue behind which can lead to long-term medical problems. Suffice it to say that I believe a properly done root canal is a medically sound procedure which is beneficial to you when it is reasonably necessary, with the only alternative being the removal of the affected tooth. I say “reasonably necessary”, because there are dentists who believe in doing root canals prophylactically under certain circumstances.
“Prophylactic” root canals are those root canals done to facilitate some other dental procedure. For example, some dentists believe that when a tooth needs a dental crown (the covering placed over a tooth), it should always get a root canal first. Proponents of this believe doing a root canal is justified for a variety of reasons. Sometimes it is so a retaining post can be placed deep inside the tooth to better hold up the crown ultimately glued to it. Some dentists also believe it is best to do a root canal before any crown is done on a tooth or even just to make an otherwise sensitive tooth not sensitive anymore. There are rare cases where these situations are justified, but I do think they are very rare. I do not believe a tooth should have a root canal procedure unless it is absolutely indicated (pain, obvious x-ray signs, a cavity is followed into the nerve by a dentist doing a filling, etc.) and no other alternatives are available besides removing the tooth. This is why I would never recommend a root canal to a patient simply so that I can place a post inside it and I would certainly not recommend it prophylactically as an adjunct to a dental crown. Each case is different, but I have not discovered any justification for these types of latter root canals and a second opinion is advisable if your dentist cites these reasons as justification. The best rule of thumb is if your tooth has absolutely no symptoms and your dentist recommends a root canal, ask lots of questions. If you are not satisfied with the answers or your instincts are nagging you, get a second opinion. Remember that a lack of symptoms does not mean a lack of problems, so don’t assume your dentist is lying to you just because you can’t feel anything.