Answer : It depends on your personal circumstances. If you have children or a partner who you don't want to walk in on you while you're in the bedroom, then it might be a good idea to have a lock on your bedroom door.
But if you live alone and feel like you need privacy, then there's no real need for a lock. Having a lock on your bedroom door can make you feel more insecure and vulnerable because it could mean that someone is trying to invade your privacy. So it's really up to each individual to decide what's best for them.