You may have read about a Failed Botox Cosmetic operation in blogs and celebrity gossip magazines; or heard about it from your friends. Same for the uncontrolled changes in a project that affect its scope. You plan to do something, and when you proceed with it, many new requirements are added to it, until at last, you end up with an entirely new product.

This what we call scope creep in project management; and what I (personally) call it a failed project’s Botox operation.

Why? - Need for Better Results.
In cosmetic operations, when a wrinkle in the skin is typically formed perpendicular to a contracting muscle located directly beneath it, Botox Cosmetic is injected into muscles (to blocks its' nerve impulses) to get smoother look results.

Same for the project management, scope creeping (also known as requirement creeping) is nothing other than customer's interference or team/project manager uncontrolled intervention to the scope management

Let’s go deep to find the real reasons for the scope creep:

First, the client Interference;
Second, the incomplete scope statement;
Third, poor change control system;
Fourth, the miscommunication among the team members;
Fifth, the external factors (e.g. market conditions, regulatory requirements, or technological advancements,etc…).
How? - Introducing new changes
The misuse of Botox can result in what many call a "frozen face" (a condition that ends up highlighting the procedure rather than wrinkles it to conceal).

Same for the improper implementation of scope management resulted from adding extra functions (features) to the product (either knowingly or unknowingly) without having those changes stated in the scope statement will lead to poison the entire project (with High-Impact-Risks).

Then... - The ugly operation and the bad results
Adding imperfectly introduced changes to the project (not stated in the scope statement) might produce many problems in the project. And this will drive you and the project team to take corrective actions by implement other changes to cover-up the uncontrolled changes made at the earlier stage.

So! - Let’s avoid it
Those project scope changes are considered bad for project health, and they must be avoided to ensure a safe & robust project management process.

Let’s start from this… “Scope creep occurs when the scope of a product is changed, and the project budget and schedule remain unchanged.”; so how to avoid it?

First of all, use a robust change control system; and never allow changes without proper review and approval.
Second, establish a proper communication channel between the client, you, and the team(to let the client talk directly to your project team members) and encourage good communication among the team members (build & support an open-minded-culture).
Third, prepare a solid and complete scope statement, and
Finally, keep proper checks on the project’s progress.
Conclusion
The rule is simple. We don’t have scope creep (the ugly Project‘s Botox Operation) if the scope (and the schedule and budget accordingly) is changed and recorded properly in a change control system.

Finally, you have to choose between the Ugly operation and the Healthy one. And your choice will maximize or minimize your project success in the project. And keep in mind, continuous-bad-practices (such as scope creeping) become a behavioural issue over time.