Way too many people just seek out deals. I appreciate we all want to save a bit of money, but someone sees a half price deal online, think "that got good reviews, and must be better than what I have as it's more expensive", and pulls the trigger thinking it'll be their be all and end all. Initially, it's the 'kid with a new toy syndrome', but once that wears off they start getting bored with it - could be because it's not right for the system, not right for their preferences, or any other number of reasons. So the hunt is on again.
If you don't choose something carefully, it's not going to fulfil your desires for very long. And if your system isn't where it should be, you'll always be searching for better stuff until you reach that point. It doesn't have to be a particularly expensive system or "ultra high-end", just one that meets your requirements and preferences in order to enjoy it.
And this way of "upgrading" just messes up the whole market/industry. Way more second hand stuff on the market (meaning you'll lose more on your unwanted item), which also draws more people into the above cycle, less new sales for dealers (so dealers numbers start dwindling). The only real benefit from it all is cheaper second hand prices.