“If it ain’t broke, don’t fix it.”
See if you can find anyone telling you why Simplex is better. “It’s faster and extends to multiple dimensions” and “simplex noise attempts to reduce the complexity of higher dimensional noise functions” were what I found. Most of us work in 2 or 3 dimensions, maybe 4 if we’re lucky enough to be doing something with time.
I think its fair to say there is little enough real-time usage of Perlin that is too slow to handle, that for most purposes standard Perlin noise is sufficient. In pre-renderings (such as used in the movie industry) time isn’t really important since renderings are slow anyway; and in real-time simulations, we have enough ways to reduce the scope of ongoing processing that it’s unlikely you’re going to be generating massive noise maps every few nano/milliseconds — that’s just basic real-time optimisation.