Iona Heath, general practitioner from London comments on this issue in BMJ:

"I learnt recently from senior nursing colleagues that sitting on a patient’s bed, by either visitors or clinicians, is now also prohibited, apparently in the interests of infection control. A quick internet search of "sitting on the bed" and "infection control" produces a huge list of leaflets from a variety of hospitals, each reinforcing the prohibition.

Doctors should never be discouraged from sitting, because patients consistently estimate that they have been given more time when the doctor sits down rather than stands. Standing makes the conversation seem hurried even when it is not; and, in the hospital setting, sitting on the chair does not seem to work nearly as well, because the levels are somehow all wrong."