Actually, they DO check.
On financial matters, the auditor general makes regular checks on ministries and departments. Stat-boards, less so, but after they did it to EDB this year and found some irregularities, I think we can expect them to be more proactive about it in future.
My friends in the public service told me once that some calls to the departments are actually fellow public officers in disguise and if u don't deal with them properly, the dept will kena thunderbolt

The ministers and the cabinet is really not the same as the ministry and the departments. public officers need to work to make sure they get the full share of their 2.5 mths bonus. If they kena "bang" over such issues and get poor performance, they stand to lose a lot.