Graphics technology continues to advance at a brisk pace, and as months become years even a top-of-the-line pixel-pusher devolves into a min-spec water-treader. Sure, that older card can technically run the latest games, but its performance decreases with every passing month. From a gaming experience perspective, though, this can be a mistake. The problem is, GPUs feel like a major investment, so you're often tempted to stick with old faithful as long as possible, extracting, it feels like, the maximum bang for your buck.
When it comes to gaming PCs - real ones, not repurposed college laptops forced to run Overwatch, badly - graphics cards are often the most expensive component in the box.