Why don't Windows 7 bootable sticks start on MacBook? On Macbook air ~2014 when I created the bootcamp partition and the Windows bootable stick, it made a stick that can start an install just fine on Windows computers.

Why doesn't that bootable stick start anymore on Mac after the botcamp partition has been deleted? What special setup does that bootcamp do on the partitions/setup process ? 

Can I re-create the proper environment with a partition manager starting with the blank hard disk ?

I tried erasing all paritions and then try to boot from that windows stick that bootcamp created but it doesn't boot a Mac anymore (boots fine on PC).
The USB stick cannot boot on Mac without Bootcamp. The Windows expects a BIOS, but Mac has EFI. That's why you cannot boot from that USB stick.