These allocators often have higher startup cost. They are designed for high performance in the steady state, but they can be worse in workloads that start a million short-lived processes in the unix style.
Oh, interesting. If that's the case, I can see why that'd be a bummer for short-lived command line tools. "Makes ls run 10x slower" would not be well received. OTOH, FreeBSD uses it by default, and it's not known for being a sluggish OS.