We have all heard this question in a job interview, either when interviewing for a job as the candidate or we have asked it as the interviewer. Indeed, "what's your biggest weakness?" or sometimes, "what are THREE of your biggest weaknesses?" is still one of the most commonly asked questions in job interviews. It is so common that many recruiters and hiring managers just keep asking it in the interviews without ever stopping to think of its purpose.
Anyone who has ever posted a job advertisement knows that the majority of the received applications are not going to fit the role. Some are too junior, some way too senior, some don't mention the basic skills required for the job, and some don't meet any standards of a well-written job application. Also, if you have ever done this, you know how extremely time-consuming it is to screen 200+ applications.