Everyone has their preferences, but many folks are tight on funds yet still want to travel the world. Riding a relatively small dirt bike when traveling in the third world has a lot more positives than you list. Especially when fitted with a larger fuel tank and relatively light weight soft saddlebags.

I can follow the pizza bikes threading through rush hour traffic in the busy capitol cities.

It is easy to hop the curb and ride up the steps of a guest house to park in the lobby.

So much easier to park in a room with outside access through a narrow door for the night.

Easier to lift into a canoe when the bridge is out.

Easier to blend in with the locals and get waved through military roadblocks.

People think you are poor so less gringo tax in Central America when negotiating room rates etc.

Cheaper to buy tires for and easier to find.

Less oil at 5.00/quart doing oil changes every few thousand miles.

Way cheaper to buy.

Easier to sell in the third world and fly home.

Easy to pick up.

Easier to ride down goat trails that a big lardy bike would choke on.

Now if you are a large person or are riding mainly in developed countries in Europe or North America on improved highways, then yes a bigger bike makes sense.
Small bikes aren't for everyone. I thought they were lame until I tried one. It helps if you are short on funds and not too bright.

There is no perfect bike.

Kindest regards,
John Downs

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South America and back on a 250 Super Sherpa Minimalist Adventure http://advrider.com/forums/showthread.php?t=831076