Well my point is not to belittle your question, but to a certain extent remind that every scientific construct has core values that really don't have theoretical justification, they just are that way. Of course, we might postulate something more fundamental, but that too will have said core values.
But I think I should point out that in the case of the speed of light the question isn't so much why the speed of light is 299,792,458 m/s rather why every other speed is X fraction of the speed of light? The speed of light is the most fundamental speed in the universe.
Again, I wouldn't mind someone figuring it out and telling us all "Why the speed of light is so". Don't worry, I'm not a speed of light denier
And... yes, that is a very interesting question. I would think it would have to do with Massenergy equivalence... but I suck at science, so I am probably wrong, lol.
Are you satisfied with the value of pi? It's the same sort of thing.
We don't know the value of Pi.
Anyway, all i'm saying is that things taken for granted should be investigated to learn the reasons for what they are, even if it is a fruitless endeavor.