There wide in certain areas other areas they are so small the cars have to wait. Have you ever been inside an apartment complex before it's as narrow as a walkway. You must be speaking of places around Tiananmen they are wide but come on that's where the president and important officials stay. Also you have to remember this is China it has the biggest population on Earth so they make it wide for those types of reasons more motorists on the road here.

Most capital cities have wide roads. They are supposed to look grand and representative.

Wide roads also assist military movements and prevent you from building barricades.

These ideas of urban planning go back to Hausmann's renovation of Paris in the 19th century; it is not a Chinese thing. 

convenient for leadership go on a journey and traffic control, you know
 
 

So tank parades look more grand. At least that's the reason the soviets did it. I heard china just copied soviets...

I honestly don't know! I've only been to Beijing twice and both of those were airport only.

I would imagine the same as most Capital cities, they look good and are impressive. Most nations want their Capital to be grand looking.

where are you from its very simple they don have streets like the s when you go to lax you can take the 405 the 91 the 105 the 60 the 210 the 10 the 5  many different freeways and streets sepulvada century slason washington and if yo add up all those lanes it would be arond 50 lanes and their are many more ways in beijing their is only a few ways to get to the airport

17 million people in one city next to a city with 9 million people just down the road from four more cities with 10 million people?