If you would have any actual experience with meditation, you would quickly notice that it actually improves focus and mental ability, regulates mood, etc. In fact, it makes a person more effective, not less. If someone meditates properly, they will achieve more and more easily, if they meditate 1 hour and then work for 7 hours - than if they would just work for 8 hours.

This assumes of course that they have any use of their brain during their work - ie, if they are creatives or mental workers, etc. If they stand at a factory pressing the same 3 buttons all day - then probably no, meditation will not help much.