There are many obvious reasons why lights should not be put in the ceiling -- the unpleasant effect of hot bright light drilling into the top of your head, the inability to move them, problems when they stop working, fire, raking shadows, the "architect's grid" or "ceiling acne" when downlighters are arranged so as to provide a flat hard light that ignores what is being done in the room, and where. To name a few! But the most compelling reason is environmental.
Illuminance obeys the inverse square law: the quantity of light varies inversely with the square of the distance between the source and the surface receiving its light.
So, if the light source is moved three times further away from a surface, nine times as much light is needed to achieve the same lux level on that surface.
Put another way, a light source on the ceiling, 210cm from the table top, uses NINE TIMES as much energy as a light source 70cm from the table top.
Therefore, by putting a light in the ceiling, you are putting it as far away as possible, and so maximizing the waste of energy.
That it is always possible to put the light somewhere suitable is proved by this picture:
This is Album's unique Radiale system. They provide a selection of (beautifully designed) lighting bodies that perform all the major functions -- radiant, spot, task --, all of which you can see being used properly here. The concept is simple: each lighting body is attached to a long thin cable that goes back to an elegant transformer (in the shape of a disc) on the wall. They also supply a hook on the cable so, by screwing the hook into a suitable location, the light can hang down exactly where it is required.
In this particular location, their system also provides light at night to replace the light that comes from the skylight during the day, without blocking the skylight. (By the way, they are also one of the few decorative lighting companies to be creating really excellent LED lights.)
Of course, there are situations where it is appropriate to put a light in a ceiling. A good lighting designer will position light sources where they are required, always driven by what is being done in the space, and where.