Because gamers were throwing their money at games long before the industry started pushing HD graphics.
In 2000, a widly successful game moved a million units. Today, a game that sells 4.5 million units is called "below expectations." The industry found that with the inclusion of shiny graphics, it could pull in much larger numbers of people than before, growing the gamer base incrementally. While production costs ballooned, the number of people buying games also skyrocketed. Games which didn't push graphic envelopes were considered niche products and developers/publishers realized real money could be made via the Hollywood blockbuster route, creating a highly visually stunning product, promoting the snot out of it and cashing in on the most number of people showing up on release day.
This led to many mid-tier studios going bankrupt, as they found maintaining the status quo in terms of visuals resulted in no one buying their games and, in a three to five year cycle, developers without extremely deep pockets went out of business by the scores or were acquired by today's monolith publishers, who in turn pushed graphics and appearances on these studios most previously popular IPs.
Flash-forward to today, where previous geniuses of game design who don't want to participate in this self-perpetuatuing cycle are now essentially forced to use the social media equivalent to a cardboard "will develop for $" sign and the only reason to get a next-gen console isn't what new mechanics, areas or features can be used with nearly four times the RAM and processing capability, but only how close to PCs the shiny graphics will get. Run on sentence FTMFW.
For those of us who have been consumers of the industry for decades, it isn't an isolated experience to feel that industry innovation slowed to molasses in the 2000's, even regressed in some cases. The cost of making video games turned it into a very expensive, risky endeavour. Meanwhile, the increasing revenues seen for the top selling games each year made it attractive for publishers and corporations to take an interest into how the games were developed to maximize their audience.
All of that bums me out.