Arcade Emulation Q's

An arcade emulation question...
It strikes me as odd that we have not seen more work on Mame, or any other PSP arcade emulator, for that matter.
How is it that Digital Eclipse can create two excellent compilations in Midway Arcade Treasures and Capcom Classics, with full emulation of arcade boards up to CPS1 and Mortal Kombat chipsets, yet homebrew wise we have a handful of Mame emulators that came out in the early days of PSP homebrew and nothing since?
I thought maybe these commercial titles were simulations, but I own a number of the actual arcade boards featured on Capcom Classics, and I am convinced they are emulated - take Strider for example.
On one of the frames of animation, a small block of gfx appears in the corner of Striders animation frame - I have this exact same thing on my Jamma board and thought it was corruption, but there it is, emulated on the PSP!
If you take into account Sony's 222mhz speed restriction, it is even stranger, with the majority of homebrew efforts struggling to run stuff like this at 333mhz, yet apparently these are running at 222mhz as dictated by Sony!
Is it a case of commercial time and money getting better results, and if so, could someone hack these titles and use the code to run other games from the same boardsets? (eg Ghouls 'N Ghosts, SF2, Mercs).
Don't get wrong, I really appreciate all the hard work of PSP coders, and love the Homebrew, but I just wondered...
So, what do others here think???
cawley1

Mame is REALLY bloated trying to support all the arcade games in existence making it very hard to port to a lower end system (and playable) without reverting back to the early builds where it only supported a small number of games. For example the GP2X/GP32 Mame port is based on ver0.34. The RAM limitation doesn't help matters either

The collections (Capcom and Midway) are most likely ports using the same media resources as the arcade.

Porting something like Final Burn Alpha would probably be the best way to go as it is target to a speific range of arcade machines (CPS1, CPS2 and Neo Geo) but again the RAM limit hurts as well.

Another factor is the firmware war with Sony is not really very encouraging to developers wanting to develop for the system.