Most people were playing SNES via composite video or RF out. MiSTER is going to be using RGB. RGB cables for SNES didn't really happen in the US (YPbPr component video seemed to come out with DVDs, and there weren't contemporaneous cables for that for SNES, although they exist now), but S-Video was available and is much better than composite.
On speakers, it's pretty simple. Physical depth is very useful for simple speaker designs, and today's screens are very thin and try not to have a bezel. It's pretty common for speakers to be downward or rear facing to make the front of the tv beautiful. This provides sound, but it's not very good. And you can't get much bass out of a small speaker anyway. A CRT tv was pretty big, adding a sizable speaker wasn't a big deal. Even early flat screens had room for an OK speaker, usually oval to use the width of the screen without adding much to the height.
Yeah, I'm not claiming that my HDMI setup for the MiSTer is the most accurate to the original experience, I'm claiming that I just like the raw HDMI output better than I liked the composite/S-Video signal. It's just a much clearer picture, I like the sharp, chunky pixels.
Yeah, I figured it had something to do with how thin they are.
On speakers, it's pretty simple. Physical depth is very useful for simple speaker designs, and today's screens are very thin and try not to have a bezel. It's pretty common for speakers to be downward or rear facing to make the front of the tv beautiful. This provides sound, but it's not very good. And you can't get much bass out of a small speaker anyway. A CRT tv was pretty big, adding a sizable speaker wasn't a big deal. Even early flat screens had room for an OK speaker, usually oval to use the width of the screen without adding much to the height.