because ent_remove dosn't remove entity completely and some data remain in memory. I wrote a program and check it.
Then prove it and post this program in the bug secetion. If ptr_remove wouldn't free all the memory this would clearly be a bug that needed fixing.
As you posted about this topic numerous times I still think you have got a bug, i.e. a memory leak on your side and as long as this is the case reducing the memory footprint of your programm won't help you.