You forget that audio is a very niche market and from a design perspective, its easier to add a switch and extra inputs to a $280 piece of gear than a $500+ product.
Audiophiles are very picky about part quality. I mean most don't even care about design, but just how expensive the Capacitors in their gear are.
In design, adding in a 0.50c part translates into a $5 increase in retail price; but you can't just add in cheap inputs into a $500+ amp when Audiophiles are running around with silver cryo'd cables worth $100 and DAC's worth $500+. It'd impose a sense of cheapness in the design when you'd expect "Hi-Fi quality" components in a product. You'd have to get silver plated inputs with a decent switch (which I assume isn't cheap). In a niche market, you're already trying to compete with the small market that you have by trying to keep costs low. I'm bad at writing up a discussion, but do you get my point?
A good example of my point is the M-Stage and the Lehmann Cube. Both follow the same design, but why do you think the Lehmann Cube costs $1000+ compared to the M-stage's $280? Its because the engineers that built the Cube spent an extravagant amount on part quality (you can tell from the Lehmann inputs vs the M-stage inputs) and ended up having to increase the price by a significant margin in order to cover costs and make a decent profit. Tom (I think that's his name) had a stroke of common sense and decided to tweak part quality to something that was worth spending on.
In Low to Mid-Fi, most people expect decent flexibility with decent functionality. In Hi-Fi, people would expect fine-tuned refinement. It'd be cheaper and a more cost-effective design to just give them one set of inputs, and let them source the fancy or not so fancy(if they know their stuff) switchbox if they need extra inputs.
Considering the Corda Swing was worth $300, Jan didn't like it when his new amp had to sell at $500 to get profit. But what could the guy do? His design had overheating problems but in order to keep costs down he has to use the same case design and machine vents into it (which doesn't look cheap judging from how the case looks) =/
Cowon J3 -> Vsonic R02ProII | B2 | T50P
DACMagic -> Matrix M-stage -> DT250 | AD900 | MS-1 | A2