Only a few have, and even then only for a few fixed things. They have extreme versions of the inflexibility problems that fpgas have, and few exchanges have low enough jitter to justify ASICS over fpgas.

It might surprise people that relatively few hfts do latency arb (and the ones that do often have some other structural advantage), and at that the ones are more and more mixing in serious short-term alpha. In that context speed is simply becoming table stakes for playing the game, and not the one true race to win it all.