Why did the orphans in the old house never have much to eat?

The orphans never had enough to eat because the old woman who was paid to care for them misappropriated the funds that she was allocated.

Sevenpence-halfpenny’s worth per week is a good round diet for a child; a great deal may be got for sevenpence-halfpenny, quite enough to overload its stomach, and make it uncomfortable. The elderly female was a woman of wisdom and experience; she knew what was good for children; and she had a very accurate perception of what was good for herself. So, she appropriated the greater part of the weekly stipend to her own use, and consigned the rising parochial generation to even a shorter allowance than was originally provided for them. Thereby finding in the lowest depth a deeper still; and proving herself a very great experimental philosopher.