Zero hour (con)tracts

Zero-hour employment contracts are on the increase.  I wonder why?

Is it perhaps because they appear to by-pass many of the benefits and rules in place designed to protect employees?

How much holiday pay is an employee entitled to under a zero-hour contract?  For an employee with normal working hours (zero) a week’s pay is the amount payable under the contract of employment – so £nil.  A similar amount may also be due for redundancy.