My reading suggests that the problem is not ATC taking sickies, nor is ATC holding the travelling public hostage.
An Australian-domiciled pilot said to me a couple of weeks ago 'there's an element of CFMEU-style tactics in what the Sydney air traffic controllers are doing'.
Sickies appear to peak on Fridays and Saturdays, and during school holidays. Amazing.
No one denies controlling aircraft must be a very stressful, fast paced job. I once worked with a male who was bright, but had applied and been rejected because he couldn't get his head around the multiple types of separation needed to be able to process.
However many other jobs are arguably equally stressful: paramedics, surgeons, emergency department nurses, train controllers, firemen at times, police, dangling from the Bolte Bridge in Melbourne to remove graffiti painted by Pam The Bird, crane operators on building sites, heavy vehicle drivers to name a few.
These people signed up for very well remunerated positions in Sydney yet it seems taking sickies (of which they have an unlimited number available each year) is hugely disadvantaging passengers, and causing airlines to waste fuel. On occasion, restricted numbers of movements beyond hourly and quarter hour movement limitations may see airline crews having to spend an overnight away from where their roster says they should be.