Questions & Answers about hoeuiga ajik an kkeutnasseoyo.
Because 끝나다 is an intransitive verb meaning to end / to be over.
In this sentence, 회의 is the thing that is ending, so it is the subject:
- 회의가 끝났어요 = The meeting ended / The meeting is over
If you used 을/를, it would suggest that something is being acted on directly, but 끝나다 does not take a direct object.
A useful comparison:
- 회의가 끝났어요 = The meeting ended
- 회의를 끝냈어요 = (Someone) ended/finished the meeting
That second sentence uses 끝내다, which is transitive.
These two are a very common pair:
- 끝나다 = to end, to be finished, to be over
- intransitive
- 끝내다 = to end something, to finish something
- transitive
So:
- 회의가 끝났어요 = The meeting ended
- 회의를 끝냈어요 = Someone finished/ended the meeting
In your sentence, 회의가 아직 안 끝났어요, the idea is that the meeting itself is not over yet, so 끝나다 is the correct verb.