What is wrong with the need to be needed though?
An emotionally-healthy adult wants a relationship with another emotionally-healthy adult. Someone who wants their partner to be needy, OTOH, is demonstrating they would prefer:
A partner who is less likely to have the confidence to leave the relationship. This means they will put up with a higher level of abuse/control/restriction rather than be single
To create a debt of obligation: if the "needy" partner is always being supported by the need-loving partner, then they are more likely to feel they "owe" the NL partner a relationship.
The NL partner is likely to have a vested interest in encouraging and even exaggerating the needy partner's insecurities and fears, in order to keep them dependent. This is totally counter to what a loving, healthy relationship does -- which is encourage you to overcome fears and grow as a person.
It creates a dynamic which is more parent-child (one party relying on the other to have their needs met) than adult-adult. This is unhealthy and immature.
It creates a restrictive dynamic -- the NL person will encourage the needy person to turn in to the relationship and shut out the rest of the world. The NL person wants to feel like they can supply all their partner's emotional needs, and hence discourage family, work and friendship connections. Over time, this becomes very isolating.
A person who is 'needy' (not just from time-to-time, like everyone is, but as a consistent character trait) needs to work on being able to fulfill their own needs for validation, self-belief and comfort, rather than finding someone else to become complicit in their dynamic.