Imagine going down to the local shops and buying a cake for $2 then going down to the people and asking them to write on it. They would have to only charge you for the writing. They don't want to lose money so they make you buy one from them
See, the problem with pranks like the first one is that people just assume it's some kinda novelty message for a laugh. Because no actual criminal is gonna phone them up and make it that obvious. That's why that kinda prank call is generally not funny and generally gets no real reaction. If you're gonna do a prank like that there needs to be some factor introduced to make it seem more genuine, like sirens or general police chaos in the background (rather then just saying "I can't be seen", which is too vague to really mean anything) otherwise people just assume it's some guy wanting a message for a funny novelty cake.
