I didn't say that eprom based speedup hacks never made it into the arcade, I said that the hack used in mame never did.
Eprom buring isn't free, it costs money. Pre-burned chips also can cost quite a bit. The hardware hacks are very cheap while a burning service isn't. Enough said.
You haven't seen the hardware hack in years, because guess what? Those games are 25 to 30 years old! When people get ahold of a pacman pcb it usually needs repaired anyway, so they go ahead and get the hacked chips as their chips are corrupted. (Why I don't know. It seems stupid to me to go to all the trouble of getting an original arcade machine just to fudge it up with some stuipd cheating hack.)
We don't really care about stuff for homebrew guys that came out within the last 10 years or so. Mame tries to emulate the roms (note I said roms, not eprom add-ons or speed-up kits) that were found in the machine, in the arcades, when the machine was in the arcades. When a real rom kit for galaga is found it'll be put it, but as of now there aren't any dumped.