Most people who have ever loved someone or had a crush on someone understand the pain of rejection very well. It hurts to know that someone you're interested in doesn't feel the same way about you.
Enter the friend zone, a term used to describe a situation where one person has unrequited feelings for another, while the other person typically sees one with feelings as nothing more than a friend. Put simply, it is a form of rejection. Often, it is seen as something a girl does to a guy, but it can very much be the other way around.
A common complaint from people in the friend zone is that they feel they are being used in the relationship, and not getting anything out of it because the other person only wants to be friends. There are entire books dedicated on how one can get out of the friend zone.
But the thing is, nobody should be shamed and made to feel like they are wrong for not wanting to be in a romantic or sexual relationship with someone else. Even if you buy someone lunch every day, take care of them when they are sick, give them rides, and let them cry on your shoulder about their own relationship woes, that does not mean they are entitled to be your boyfriend or girlfriend if that isn't what they want. It does not mean that you deserve for them to be your lover. In fact, doing all these things with the sole intention of getting "past" the friend zone and into their pants rather than doing it because you care about them does not make you a great friend.
The idea of friend zoning as a negative thing also implies that friendships are inferior to romantic relationships. While being someone's friend is very different from being their love interest, it does not mean that your relationship with them isn't valuable. I love my friends and people's relationships with their friends is complex and nuanced. Some people hold their friends in greater importance than their boyfriend or girlfriend, especially if they've known their friends longer.
Sometimes, friendships may develop into something else, but other times they never may. If someone says they're only interested in being friends with you, it is better not to bother them, make them feel bad about it, badger them about their relationship choices, pay for their meals in the hopes that they'll change their minds and then complain when they don't, or any other thing that society has implied it is acceptable to do upon romantic rejection.