Why are there so many preparatory schools and cram schools?

Japan is probably the country with the largest number of preparatory schools in the world.
Although in some countries including France and the United Kingdom, entrance or qualifying examinations for advanced schools are verv hard, no other countries have juku, or cram schools, even for entering prestigious private kindergartens.
Some Japanese parents are eager to send their children to such kindergartens which are affiliated with universities, which in most cases guarantees that the students can go on all the way to the universities, which are also considered prestigious.
Many students, ranging from elementary school pupils to those who make a second try to enter colleges, go to juku to prepare themselves to successfully pass entrance exanimations.
The reason is clear.
Just attending regular schools is not enough to survive in the examination war in terms of obtaining the knowledge necessary to be successful.
A society with a heavy emphasis on one's academic career, in which graduating from first-rate universities is among the first requirements to get quickly promoted, is behind all this obsession.
In recent years, the rapid decline in the number of children has made it necessary for preparatory and cram schools to fight for survival.
Some schools maintain their numbers by boasting of high success rates and their own curriculums、but at other schools fewer students means a drop in academic levels - and that is what decides the school's fate.