No problem actually.

Bst/ast has a lot of inefficiencies and train too few and too slow


1) inefficiency
After completing bst, you must go find your own ast. If there is no ast position available, you had to wait and serve as a service reg until ast position opens.

With residency is through train. No need go worry abt bst and ast. Once you are R1 u usually can go to R5/6 without issue. Residency is more efficient, (no year loss as service reg).

2) planning and bidding for postings
Furthermore during bst, you had to plan your postings and bid for mopex.
In residency system, the postings are preallocated to you. Failure to bid successfully for a certain mopex delays completion of bst.

3) initiative needed
Bst and ast needs more initiative from the trainee.
residency is actually very structured. U get a program directors. Bst ast you have to fend for yourselves

4) opportunities for training
It was harder to get into bst/ast than residency. As there was lesser slots than now

5) job opportunities
Residencies are easier to get in. Bad thing is residency numbers are centrally controlled. Central planning means they will overrecruit. And at end of 5 years, u will find no job coz they opened too much positions. But at least it was easy to get into residency

AST is employed by hospital. So a hospital dept knows exactly how much manpower it needs. So you get a job at the end. but a hospital may underproject and you may lack specialist if the seniors decide to move to pte en-masse.