In most of the work places, interviews are the entry barrier to become a part of an organization. The general tendency of anyone to approach an interview is to do it like an examination. An evening or two of preparation especially if it is a technical job and some search on the net for answering typical questions gives an illusion of being prepared for an interview. It is easy to get through examinations with an overnight of preparation as only the factual accuracy of the answer matters.
Interviews in my opinion are more of discussions than question answer sessions like exams. For technical jobs, the interviews will be centered around the sound understanding of the fundamentals and application of that knowledge rather than checking the memory of first page search result answers for the questions. If the attitude and approach towards a day job is inclined towards continuous learning and improvement, then that may help a lot at an interview than an overnight preparation. In other words we should be able to meet an employer on a flight journey, conference or social events and stumble on a job offer without any preparation.
Being employable is analogous to being physically strong. Just like how one should exercise every day to be fit and strong, the learnings and applications every day at workplace helps in strengthening our capabilities. It will also not come to us in a few days, it is a long and continuous process which should become a habit.