When you're single, you can talk to whoever you want at the bar, swipe left and right all day long, and do whatever your heart desires. A relationship is likely to constrain one's freedom of choice and giving up that freedom is difficult for some.

People who are very connected to their peers are going to go along with the morals and community rules set by this group. And if this group is all about being single, and they frown on couples who are committed, getting into a commitment will mean losing the approval of this peer group.

When a relationship goes sour, it can be hard to get over. And some take time to be single for a bit. Distaste from a previous or current relationship can be enough to keep someone from committing to a new relationship in the future.

The idea of a commitment to this person seems like misery. Especially if they had a series of bad partners.

Some fear commitment because they are afraid that the relationship will be so good, that when their partner abandons them, it will be unbearably painful. 

Divorce can be soul-crushing and those who go through it are often afraid of commitment because they worry it will lead to another divorce down the line.

Some value independence more than a relationship. They don't want to have to answer to good or consider anyone when it comes to deciding things so commitment becomes unattractive.

If you or your partner fear each other's family and friends, this may become an obstacle to a healthy, happy relationship and lead to fear of commitment.