Why do some people make their Instagram accounts private?

To avoid being followed by strangers

Some people dislike being followed by people they don’t know, so they make their accounts private.
They don’t want certain people to see their accounts

Some people try to hide their social media accounts from some people. Making their Instagram private helps with that.
They like being in control

People who like being in control can make their Instagram private so that they control who can see their posts.
They are celebrities

Some celebrities make their personal Instagram accounts private so that fans don’t invade their account. (See Why do celebrities use Instagram?)
They want to post pictures freely

Some people make their Instagram account private so that they can post whatever kind of pictures they want.
To avoid being followed by spam accounts

Making your Instagram account private ensures that you don’t get followed by spam accounts.
To avoid having their pictures stolen

Some people suffer from having their pictures stolen and people creating fake profiles with them. Making Instagram private prevents that problem from happening.
They don’t want people to know about their private lives

Some people appreciate privacy, which is why they choose not to make their Instagram public. (See Why Do People Care About Online Privacy?)
To avoid harassment

Some people experience harassment on Instagram due to their sharing certain photos. This drives people to make their accounts private.
To hide it from their family

Some people make their Instagram accounts private so that their family can’t follow them.
They don’t care about the number of followers

Some people create Instagram accounts to share pictures with a close group of friends. They don’t pay much attention to their number of followers.
To not be judged by people

Some people hate being judged by others. Making their Instagram private is one way of avoiding judgment.