Well yeah, RPG speedruns are typically pretty boring. They can get somewhat exciting if the speedrunner discovers a new strategy or exploit that works particularly well, but in general they're not very fun either to make or to watch. You'll also notice that
Speed Demos Archive has very few RPGs for this very reason.
On the other hand, platformers lend themselves very well to speedrunning. The primary challenges are typically in route planning and careful execution. For example, in a classic Sonic game speedrun, a lot of thought goes into deciding whether to take the upper or lower route in each level, or even to switch between them where it's worth more time. The speedrunner must take into account the length of the path, the number of obstacles and enemies, how easy those obstacles/enemies are to avoid, whether it's faster to just take damage rather than avoiding, what TYPE of obstacles there are, and much, much more.
After what often amounts to
weeks of planning and prep work, as well as possibly dozens or more of test runs, the actual speedrun attempt(s) require a tremendous amount of precision. A slightly mistimed jump can cause Sonic not to clear a ledge and ram headfirst into a wall. In a game so heavily focused on momentum, the time lost can be very significant and effectively blow the run. But even barring massive run changers like that, little things such timing your jumps so that the most ground time is spent rolling downhill, or bouncing off enemies at just the right angle to gain the most forward speed, can add up over time and make a huge difference.
For me at least, a large problem with RPG speed runs is that they are inherently slow-paced and quite repetitive. It doesn't take a whole lot of skill to spam the most effective attack against a boss, and there's not a whole lot of reflexes involved in walking across the world map as efficiently as possible. The real entertainment factor in watching a good speedrun is the sheer amount of skill it takes to pull it off. One of my favorite speedruns is
this Sonic + Tails run of Sonic 3 & Knuckles. Though a few parts of it do rely on glitch abuse, for the most part it's a showcase of sheer mastery of the game; this run moreso than most because of the stellar use of teamwork with the second player controlling Tails.
Most of all, what a great speedrun should do is capture the thrill and exhilaration of a high-speed race in a non-racing game. You're never going to find this in a turn-based RPG, because they're slow as molasses. Mario 64 is closer, but his top speed is a bit low, and speedruns of that game have largely been ruined by (as you said) wall glitches. But a warpless Super Mario Bros. 3 run, or damn near any Sonic Generations run, is just plain exciting to watch, and even more exciting to make if you've got the reflexes to pull it off.
