Wikipedia:Editors have pride

When attempting to determine a course of action in dealing with a problematic editor, administrators especially should try to remember that editors have pride. They will not necessarily admit wrongdoing, nor respond well to requests that they do so before leniency is afforded to them. This does not necessarily mean that they actually intend to continue problematic activity. It may in fact be evidence of the opposite.

Typical handling of unblock requests (and other requests for reinstatement of privileges)
When an editor is blocked and requests to be unblocked, a typical admin response has often been something to the tune of:

"'If unblocked, do you agree to edit constructively?'"

This is not necessarily the course of action that is most likely to produce a constructive result.

Why this is bad
Even editors who realize they were in the wrong will have an interest in preserving their pride. Providing a satisfactory answer to the question above might feel, to the editor, like telling a parent "I promise to be good". Demanding this type of response before a block is removed is like forcing the person to beg for it. It's understandably not something most people feel comfortable doing.

Understand that the blocked individual making a sincere unblock request will consider the mere presence of their unblock request as an implication that they intend to edit constructively. They will therefore view the administrator's ultimatum as an "I want to hear you say it"; which is again a demeaning proposition, and unlikely to be met with a cooperative response from an average person.

An individual making a sincere unblock request may, additionally, already feel wronged by the block. Although they may not agree with the reason they were blocked, this does not necessarily indicate that they plan to continue perpetrating the blockable offense. An editor can respect that an action is not allowed, yet still disagree with the rule — perhaps even feel angry about it. Therefore, asking for an admission of wrongdoing is not only a similarly demeaning request, but probably not helpful in determining how the editor will edit in the future.

In fact, an editor is most likely to respond well to such an ultimatum when they have every intention of continuing their undesirable behavior. They may not particularly care about the project or its rules, and may be more interested in deceiving the administrator to regain their lost privileges as quickly as possible. The editors who care are the ones more likely to feel slighted and demeaned by this request.

Suggested alternative
Depending on the situation, a better course of action may be to lay out specific guidelines that would allow the unblock. For instance, "In order to grant this unblock, we would need for you to agree to refrain from reverting article X for Y period of time." Or, "...refrain from contact with user Z for U period of time." This lets the blocked user save face, while still allowing them to provide some assurance regarding their future behavior.