Castlevania: Symphony of the Night (or SOTN to its dear friends) was released over 15 years ago, and spawned the gametype known as 'metroidvania' - the exploration, items and RPG-like elements of Metroid, fused with the gothic styling of Castlevania. It was, to understate it slightly, fairly well received.
As the first entry in the game type, and probably hurried during production (several intended areas were only finished for the later Sega Saturn release), SOTN has a less than solid engine. There are many glitches, including out-of-bounds exploits (enabling skipping large chunks of the game), certain items which trivialise boss content, and powers which allow you to equip items as you sell them, which then gives you the maximum number of that item.
Not that later entries into the series seem to have learnt much, many similar glitches still exist.
Over the years, dedicated gamers have spent an inordinate amount of time poring over this game, finding the easiest ways to kill each boss, the fastest path through the castle, the fastest ways of moving, and even how to finish the game as a 'pacifist' - the game having credited you with no kills. And yet, even 15 years later, new ways of exploiting the engine are still being found. Only two months ago, a new world record for fastest game completion was posted (18 minutes 20 seconds), but forget about that: this past week has uncovered a new take on a glitch which saves another minute with some route changing, and no doubt more will be found in the future.
While a glitch-free game is certainly desirable in normal play, many of the games with the longest life-spans are full of bizarre bugs (see: Super Mario 64, Legend of Zelda: Ocarina of Time, SOTN). I'm sure these games would still gain attention from the speed running communities even without the glitches, and they are certainly compelling and lasting experiences without any knowledge of the glitches, but seeing the basic game rules being utterly broken is just much more cool.
Of course, the argument could be made that every game invariably is full of these glitches, but only the biggest, most popular games are explored to the extent necessary to find them.
Regardless, sometimes an imperfect engine is a far more interesting one than that with no 'flaws'.