Why would different crossing runways at one airport be on different radio frequencies? In this answer the following image was included which shows that control of two crossing runways are on different radio frequencies.


Source: AIP Denmark EK AD 2 - EKCH - AREA OF RESPONSIBILITY

It seems to me that having crossing runways on different tower frequencies could lead to a runway incursion or worse, an accident, if there is any loss of controller-to-controller communication within the tower. One of the key tenants for pilots is situational awareness, and being on a different frequency means that the pilot of an aircraft receiving clearance for take-off on 12 won't know about a plane receiving clearance for take off on 22L at the same time and thus, couldn't question the clearance.

Now, I realize that it's unlikely for both 12 and 22L to be in use at the same time, but if the winds are fairly calm and to the North, it could be possible, especially if traffic was high. However, I seem to recall some discussion here about an (near?) accident that happened on crossing runways where the pilots were unable to see each other as they began their their take-off rolls. 

My question is: Why would different, crossing runways be assigned to different tower frequencies since this can lead to a lack of situational awareness and potentially cause incidents?
That division is applicable only when the parallels (4's or 22's) are in use, which is the preferential system (see title of chart).

As for rwy 12/30, from the eAIP (PDF; link may die; homepage):

Between 6 AM and 11 PM local:


  RWY 12 and RWY 30 may be used when one or both of the preferential runways cannot be used (...)


Between 11 PM and 6 AM local:


  RWY 12 and RWY 30 are closed for take-off and landing, however, RWY 30 may be used for landings when the crosswind component on the preferential runways exceeds 15 KT or the preferential runways are not available due to disabled aircraft, snow clearance, work on the runways, etc.


Once 12/30 is in use, that chart does not apply. Further:


  During periods with low traffic intensity one or two positions may be responsible for all three area, but apron service will be provided on three separated frequencies simultaneously. The frequencies will be combined by ATC. [emphasis added]