It doesn't delete activation, all that does is wipe all your files, it still keeps the basics of windows, like it is when you first installed it. Brand new, no users, no drivers. But it knows its got a licence.
Activation is matched to the machine, so once win 10 is installed on a PC it can be reset an infinite amount of times and it will remain activated. You can fresh install win 10 onto PC and it will remain activated, You can change the motherboard on a PC and win 10 will still activate (Especially if you on build 1607 and use your Microsoft account to logon, as its automatically matched to your email address) - though you may need to do things first (see...