Did the Companions really pluck their armpit hair? I shave mine; it just seems like it would be too difficult to do so. Also, what is plucking the armpit hair good for, reducing odor?

All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.

The Prophet, sallallahu ‘alayhi wa sallam, said, "There are five acts of the Fitrah (natural human disposition): circumcision, removing the pubic hair, plucking the armpit hair, clipping the nails, and trimming the mustache." [Al-Bukhaari and Muslim] This is the wording cited in Saheeh Al-Bukhaari.

An-Nawawi wrote:

"Scholars unanimously agreed that plucking the armpit hair is an act of the Sunnah and that its due time is the same as what was mentioned regarding clipping the nails; it differs from one person to another and from one situation to another. The Sunnah is to pluck it, as explicitly stated in the hadeeth, but if one shaved it, that is permissible. Yoonus ibn ‘Abd Al-A‘la narrated that he visited Ash-Shaafi‘i once while the barber was shaving his armpit hair. Ash-Shaafi‘i remarked, 'I know that the Sunnah is to pluck it, but I cannot endure the pain.' And if one removes it with Noorah (slaked lime used for hair removal), there is no harm in that." [Al-Majmoo‘]

Hence, plucking the armpit hair is the act of the Sunnah, and it is known that the Companions, may Allah be pleased with them, were the keenest on following the example of the Prophet, sallallahu ‘alayhi wa sallam. However, what the questioner is doing of shaving the armpit hair is permissible, as mentioned above. Some scholars underlined that plucking the armpit hair reduces the unpleasant odor that might be there. Al-Munaawi wrote, "As for plucking the armpit hair, it is recommended by consensus (of scholars). The Sunnah is fulfilled by shaving it or removing it with Noorah, but plucking is better because the armpit is the cause of bad body odor, and plucking it weakens its roots and reduces its amount and accordingly reduces the bad odor (of sweat)." [Faydh Al-Qadeer]

Allah knows best.