>>monort+(OP)
Quoting astrocat from the previous thread:
PSA: Watch in an private/incognito tab/window. If you are currently logged into your google account, this WILL pollute your watched history: https://www.youtube.com/feed/history
>>human2+mh1
Others are suggesting practical reasons for having watch history enabled, but I would think that the vast majority have it enabled simply because that is the default.