Hi lally,
Do I understand you right that you want to know the reason why you do not post the depreciation against the orginal 'fixed asset acquisition' account?
I just assume that this is the case and the answer to your question is that it depends.
That is you can either post the depreciation directly against the fixed asset acq. account (net method) or use a separate accum. depreciation account (gross method).
The gross method is better because many accounting bodies require explicitly the reporting according to the gross method, which gives better insights in the fixed asset structure.
Best regards,
Ludwig