Because Jonas’s community tries to eliminate all discomfort, it is not a good idea for people to be in pain. The community uses strong painkillers for even the smallest types of physical pain. Choices are tightly controlled, so that people will not feel emotional pain.
Jonas describes the life he left at the end of the book.
The life where nothing was ever unexpected. Or inconvenient. Or unusual. The life without color, pain, or past. (ch 21, p. 165)
Interestingly enough, the exception to this rule is when the community wants to cause pain in order to punish someone.
The punishment used for small children was a regulated system of smacks with the discipline wand: a thin, flexible weapon that stung painfully when it was wielded. (ch 7, p. 54)
Apparently, it is ok to spank a child and cause pain, but it is a process only used by trained Childcare workers. However, the punishment does escalate. Asher is beaten so badly when he is three that it leaves marks on the back of his legs.
When Jonas is chosen as the Receiver of Memory, they tell him he will be in pain for the first time, and will not be able to ask for relief of pain medication.
"You have never experienced that. Yes, you have scraped your knees in falls from your bicycle. Yes, you crushed your finger in a door last year." (ch 8, p. 62)
With pain, he will acquire the wisdom he needs to advise the community. The Giver demonstrates this when he explains to Jonas that the Committee comes to him when they need advice. When they wanted to increase the population, The Giver advised them not to because he had memories of food shortages and the pain they caused, but no one else did because there is no history.
When Jonas experiences pain during the memories, he asks for medication at first. He is denied it, so he just continues to learn to live with it.
Lowry, Lois (1993-04-26). The Giver (Newbery Medal Book). Houghton Mifflin Harcourt. Kindle Edition.
Jonas lives in a bland world. Everything is moderate and highly regulated, not to mention medicated. There is no hot. No cold just in-betweens. Similarly there is no pain, or very rarely any pain. Things that are likely to cause pain are simply not allowed inside the community.