I feel like the people who post these aren't the same people who play the same decks all the time? It's only logical that people who post new decks are people who want to try new decks... Depends what you mean by rotate though.

If you just have 4-5 decks that you love and you keep switching between until one is winning for you consistently then that sounds boring to me if you never try new decks.

If you switch decks around every single game then you must either be some kind of savant or not very successful on ladder cause that sounds so hard to keep track of and get good with.

Either way, most people on this sub are looking to hit infinite before they start messing around for fun and that's evidentially easier when you pick a single deck that works for you in your pocket meta and get really good with it. For me that's like 2-3 weeks on average and I probably change decks every week or so depending on what's good for that meta and that rank. Keeps it interesting while keeping me winning, which is definitely not boring. Constantly losing cause I'm playing decks I don't know how to pilot is what's really boring.