Warning: This thread is pointless and is just me rambling about a thought that's been rolling around in my head for a while 
Having just sold a handful of bikes recently, one of the most common bargaining tactics used by potential buyer's to get me to drop the price of my bikes was that the bikes were a couple of years old (ranging from 2013 to 2015 model years) and thus not worth anything. On more than one occasion, I'd get someone sending me a link to some "bicycle blue book" stating that my bikes were worthless because they weren't the latest and greatest. I learned to ignore those potential buyers and my bikes all sold for what I was asking... thanks to COVID-19
That got me thinking... are we as a society being duped into thinking that a bike that is a few years old is now a piece of outdated junk, just because we've become used to a 2 year obsolescence cycle for electronic goods? (I.e. "
Moore's Law" has had a pretty big role in people buying a new mobile phone or computer every 2 years because that's about how long it takes before a new, much faster model is invented.) Unless you're planning on buying a bike with SRAM eTap, Shimano Di2, or some other electronic components group, the entire rest of the bike is not electronic and not subject to radical improvements from year to year.
I often think manufacturers just introduce new models with new marketing hype to convince us that the newer model is radically better than the old when it potentially is not. For example, I'm still wondering why Shimano created the Ultegra R8000 group set when it's hardly a departure from the 6800 group set. Both are 11 speed and both work just fine. It's my opinion that used bikes with Ultegra 6800 are a great value because they're perceived as being "yesterday's news" but work just as good as the new R8000 bikes.
While there certainly are incremental advances and improvements in bikes over the years, I personally think that one ought to really consider if you really
need the latest model bike or if you just
want it. There's nothing wrong with either, but if you can convince yourself that you don't need a brand new bike, you can save yourself a lot of money. Not only that, bicycles typically hold their value worse than cars do... once you ride the bike away from the LBS, you'll have a hard time selling it for anything near what you paid for it (well, excluding our current bizarro-world COVID-19 bike shortage.)
Anywho... your thoughts? Are bikes that are more than a few years old worthy of the scrap heap? Is buying a brand new bike a psychological gain or a good idea? Should we all buy a new bike every two years to keep up-to-date along with our iPhones and Android phones?
Note: I currently ride a 2020 Trek Domane SL7, so I'm a little hypocritical when it comes to my argument that one doesn't need a new bike. However, in my defense, I did buy it used for substantial cost savings... I would've stuck with my 2015 Domane had the deal not come along.