With all due respect to the pilots involved.
Why is there now a trend (King Air Essendon) for pilots to waste time giving a Mayday call when there is no one, other than themselves, who can help them. It would seem to be a lot more productive to use that time to attempt to regain control.
Probably so search and rescue can be arranged immediately. Clearly if you are near the controlled aerodrome of departure you will likely be on radar or at least being procedurally monitored, but to save thinking "is anyone likely to be watching me on radar", I guess it is good airmanship to send out a mayday regardless just in case no one is watching.