Although I do TT some (rewind to earlier in the day, go forward a couple days), I'm uncomfortable with longterm TTing that the campsite method requires because I don't want to spoil new seasons and seasonal recipes for myself. On the other hand, duping is easy to do and doesn't require TTing. I'd wager there are many people who are ok with duping but wouldn't want to do campsite TTing years through the future.
Also, campsite method is extremely time consuming. Duping is not anywhere near as much.
Btw, this method looks like it doesn't carry risks of having glitched invisible items floating about like the previous method, so I'd wager it's not risking save files or anything. A lot more accessible.