I approve a lot of them and keep a percentage for future use as well. I feel your confusuion at not being thanked and there fore not knowing if there's any point but there is my friend...most get so into the work that they forget to notify the creators that they're grateful. I, when I use a freebie or a purchaces item, always sent the maker a link to the render and a thank you at that time. I wish we could make that a stipulation for use but by requiring anything like that they're no longer really free...you pay by writing a letter...seems silly I know but that's how I see it.

 

Once in a while I look around,
I see a sound
and try to write it down
Sometimes they come out very soft
Tinkling light sound
The Sun comes up again