It is something kids love, perhaps as a way of getting one over on the grown ups. I am slightly older but still jump at the chance to make someone an April Fool given half a chance. Is this a new phonomina which has caught on in modern times ? No, it apparently goes back in Britain to the 18th century.
It was probably borrowed from the Scottish custom of sending people to "Hunt the Gowk", which is a type of cuckoo or foolish person. The traditional prank was to ask someone to deliver a sealed message that supposedly requests help of some sort. In fact, the message reads "Dinna laugh, dinna smile. Hunt the gowk another mile." The recipient, upon reading it, will explain he can only help if he first contacts another person, and sends the victim to this next person with an identical message, with the same result. I'm not entirely sure why that caught on !
I found an article from 1850 - yes, 170 years ago - from the Sherborne Mercury, which suggested it was then considered to be a dying hangover from a barbaric age carried out purely by the lower classes :
As the foolish practice of making April fools on the first day of April is still practised, not only in our country but all over the continent, and even in America among the descendants of Europeans, a few words on its origin may, perhaps, be found amusing :
Is set apart for All-fool's day ;
But why the people call it so,
Nor I nor they themselves do know."
However the most famous April Fools Day joke was on the BBC Panorama programme in 1957 when they showed a family in southern Switzerland harvesting spaghetti from the family "spaghetti tree". At the time spaghetti was relatively little-known in the UK so that many Britons were unaware that spaghetti is made from wheat flour and water. A number of viewers afterwards contacted the BBC for advice on growing their own spaghetti trees.