Why did Commodore put monochrome video output on A500/A2000?

[pwermonger]

IIRC, the reason for monochrome was that not all users needed color composite. A lot of Amiga 1000 users were buying monitors. So they could save a bit on the 500 and get the 1084 monitor and be done. Those who needed color composite, were not probably not buying the 1084 and would instead buy the A520 adapter. If the 520 wasn't available immediately whenthe 500 came out, it was available shortly thereafter.

[pwermonger]

if I had to guess, which most of us can only do in this case, I would have to guess that it was one or more of the following
 
 1. Save money on the composite out, per unit that savings could add up
 2. Push people to buy new monitors instead of hook up to existing Commodore 8 bit composite monitors or TVs which makes more money
 3. those who still want color composite buy the A520 which again makes more money.

[pwermonger]

The A500 and the A2000 were designed and build two totally separate teams, they probably didn't even know about each other.

They did know about each other, in fact Dave Haynie said he watched what the 500 team did (which he originally was put on) and copied a lot of it for the 2000 in his talk at VCFE 9.1. At least, the American designed one. Not the German designed one that it replaced.