Do they really? I think speedruns are great, but I don't think that doing that is in any way superior to just playing a game to have fun. In fact, it's really just having fun by abusing the game mechanics to their absolute limits.
In fact, when you play a game normally and when you sequence break and glitch your way across the finish line in record time, it's a totally different experience. Different things stick out and different things matter. This is true even if you do your speedruns live.