• It is lighter and cheaper, as you can use thinner materials. This is because pointy is a stronger shape than flat.
• It gives more interior space.

If you're using lighter cheaper materials you'll need all the added interior space for roof trusses, none of it will be livable space.

• It allows more sunlight to reach the street.

No, for the same amount of occupiable space the shorter flat roof blocks less light than a standard 10:12 or 12:12 roof

• It has a smaller area-to-volume-ratio through which heat can escape.

The greater surface area of a pitched roof means this is absolutely not true. The hypotenuse is always longer than either leg.

• Solar panels get a higher efficiency.

This one actually depends on latitude, equatorialy it's better flat. And don't forget that the minimum summer angle is limited by the pitched roof.

• If a city has the same height restrictions for flat roofed buildings as for pointy roofed buildings, and the architect is too lazy to go to the city council to explain to them that that doesn't make sense, the architect can design a building with more volume by making the roof flat.

No it makes perfect sense. It goes back to your comment on letting sunlight through to the street. The maximum height is the maximum height so everyone gets the same amount of light.

In other words: ~~the only reason any architect would design a building with a flat roof is because they are either lazy or they have no idea what they are doing.~~ this guy thinks their habitat is the only kind over the whole planet and can't imagine people living in areas where snow load wouldn't need to be considered.