Agile methodologies to the world of business came from the IT industry. The assumptions of "agility" are derived from the Agile Manifesto, which was to be used to develop completely new methods far from cascading project management.
By employing team members, we buy not only their skills or experience, but also their time. To make the most of it, we usually fill the proverbial eight hours entirely. Planning specialists will tell you, however, that it is not important how many hours we devote to work, but rather how affectively we use the available time.
Planning is the key word in modern management. You can see different approaches to this subject. Some plan more than they actually do, while others can be totally spontaneous. Of course, we don't recommend any of these extremes. The best solution is to look for a happy medium, but how should this be achieved?