The point you are missing is that a receiver (even with no transmitting equipment included), if in some way faulty, can act as a transmitter and block/interfere with other signals.
Regeneration of received signals is a well known phenomenon and there have been thousands of documented instances over the years of such interference.
For many years various airports in the UK banned aircraft band receivers as some makes were known to cause problems, particularly with ILS equipment. Manufacturers took note and improved the situation - but it is not possible to 100% cure it.
The problem with a regenerated signal is that it is random, will crop up on any frequency and, if the signal is regenerated in close proximity to another receiver it will cause problems with legitimate signals.
Quite often, at airports where you see a large number of enthusiasts with radios operating different frequencies but standing in close proximity, you will find someone complaining he is hearing the wrong signal, or all his signals are blocked, due to this problem.
Similar problems can occur with laptop computers. You can demonstrate this by firing up your laptop, or PC for that matter, whilst placing your radio close by.
With many, though not all, computers you will get interference whilst Windows is loading, or whilst saving documents.
Airlines try to accommodate the needs of the passenger to work or entertain themselves and balance these with the needs of safety.
Digital cameras and video recorders are a "grey" area as they use very low battery power, have no receiver or transmitter and have not been found to cause a problem. As for TV standard recording equipment, this is always checked out prior to on board use - as is the equipment used by companies recording the popular flight deck videos.