Erhm, isn't it a bit odd Konami decided to implement a soundchip in many games they released for MSX? What kind of commercial corporation decides to higher the production costs just because of the sound of a game. The PSG wasn't THAT bad.......
Suddenly crossed my mind 
Well, maybe they just did it as a try-out at first (Nemesis 2), and liked the results (or the sales) so much that they decided to continue with it. Hmm... IIRC, Nemesis 2 is from 1986, the first game with SCC. Games like Usas and Metal Gear are from 1987, without SCC, so apparently there was some decision making about what games to ship with SCC.
Makes you wonder: why didn't Konami ship games with a graphic enhancement in stead? 
What is the first MSX2 game with SCC anyway? I mean, most SCC games at the beginning were MSX1 games, whereas MSX2 games from the same period had to make do with the humble PSG. Maybe coding/pixeling for MSX2 was more expensive (more work) and there was no money left to the sound bit?
Makes you wonder: why didn't Konami ship games with a graphic enhancement in stead?
A (hardware) graphic enhancement is much harder to integrate into a game than a bit of extra sound. For sound, you just tie the sound outputs of all available sound chips together and you're done.
For video it's not that simple. The cartridge connector doesn't provide for it - no video lines, no DMA-like VRAM access (which would be useful for some graphic co-processor, eg.) ...
That implies that a video enhancement has to be provided as an extra VDP in the cartridge with its own video output connector on the cartridge (think Gfx9000). That is (1) costly and (2) poses the problem of the video output type and connector to choose. Any decision you'd make on number (2) would cut down the possible user base of your game in half. At least.
