I'm not talking about this site specifically, but in general. Obviously speedrunning is more popular on a site dedicated to speedrunning. But I'm talking more in the grander gaming sphere speed running seems to be more popular. With far wider "fringe" support, for lack of a better word, in non-gaming media like video's, articles, etc.

To use DarQ's highscore sites as a metric the general threads to speedrun.com is far more populated, roughly at a factor of 4 in the general threads. And introductions on speedrun.com outnumber those of Highscore.com and cyberscore.me.uk by a factor of around 18 (assuming new people only ever post a new thread if they are actually new). I find it weird the speedrunning is more popular while being less supported natively by games (as in the ability to compare previous runs to your current one).

Maybe the question can be better worded as "Why has speedrunning attracted more people than other forms of single player competitive gaming, especially considering more games have been build with these other forms in mind?"

I'm wondering, high scores and time trails are generally well supported by the games that have them. However it seems that very few games natively support speedrunning as most games don't keep a record on how quick you've beaten a game and compare it to previous times.

So why does it seem speedrunning is more popular than getting a high score any game with score, time trails in racing games or other such performance metric? And what makes a game good to speedrun?

Based purely on how well a game supports comparing performance metrics I would expect racing games, shmups and other arcade games would be far more popular to compare performance on, yet this doesn't seem to be the case.