One reason for that is that several of the pilots who are looking to leave are within 3 months of contract renewal. I believe they have applied for new contracts but that RBA are being very slow in processing them. The method behind the pilots apparent madness is that they are waiting (hoping) for RBA to tell them that their contracts are not being renewed, thus obliging RBA to cough up 3 months salary in lieu of notice.
Now thats the sort of business acumen that RBA ought to try to hold on to.