In response to one of the original questions, one reason a pilot may prefer to depart on a VFR clearance rather than an IFR clearance, is to avoid ATC delay.
As an IFR departure, ATC would be required to separate you from other IFR traffic they are working as an Approach unit. Due to requirements of separation, then (particularly in a Procedural ATC environment), the delays can soon mount. A VFR departure does not have the requirement to be separated by ATC, so tend not to be delayed by waiting at the holding point waiting for separation to be acheived, as an IFR departure may be.
Now whether it is desirable on safety grounds for aircraft to depart as VFR in such conditions, is a different question. It certainly doesn't fill ATC with a warm glow of 'everything is all right' when such VFR departures immediately enter IMC on departure as they have not until then been required to separate that traffic from the other known IFR traffic. Apart from the effect on the separation of the (now IFR) departure, it may have also seriously reduced the separation established between other IFR flights that ATC is responsible for separating, but hadn't been expecting to have to separate from the VFR departure.
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