In addition to DuckPaddles answer regarding
Many companies only file to be granted Provision Patents (PPs) and
each year when the Patent comes up for review they ask for it to be
put at the bottom of the pile.
This way companies dont have to pay the hundreds of thousands of
dollars until they realise the idea is good enough and wish to create
barriers to entry. More commonly is for companies to wait for
competition, issue there provisional patent then put an injunction
against a competitor.. its a dirty and expensive business.
I held 3 PP's and the Australian Patent Office and my Patent Attorney charged me about $3500 to have one of the Provisional Patent delayed. This was in 1999, I was only 20 years old and could only afford to do it once.