They always use the excuse of being too 'busy' to write their cynical branding attempt book. Which is strange because there's a bestseller by a junior doctor, Adam Kay, out called, 'This is going to Hurt' and junior doctors tend to be pretty busy people. So these celebs must be working hundreds of hours per week!
In Gemma Collins case she couldn't even be arsed to read the book that someone else had written for her. 
I'm no fan of Katie Price but to her great credit she was very open about using the late Rebecca Farnworth.