Although Microsoft has stopped Windows 10 free upgrade at the end of last month, there are more people coming and want their Windows 7 back. Those people either get used to Windows 7 or just simply don't like Windows 10. After all it looks a little bit similar to Windows 8. But the techs/geeks know, Windows 10 is way better than Windows 8.
For those people who upgraded from Windows 7, they can always downgrade back, either through Windows 10 "Settings -> Update & Security -> Recovery" if less than one month upgraded or just do a clean Windows 7 install.
However, for those new computer owners, if their computer comes with Windows 10 Home, there is no chance that they can downgrade to Windows 7 without a cost. You will find out only Professional&Ultimate Versions are able to downgrade to Windows 7 if they choose. Home premium and basic are not included.