Same reason Indy cars aren't built like off-road cars, they're meant to be used for different purposes.
Road bikes are meant to travel fast on hard, smooth surfaces, while mountain bikes are meant to travel slower on uneven, loose ground.
Different uses, different designs.
What you need to do good under one set of circumstances might not be that useful under another set of circumstances.
Yes as are most bikes these days, but not in top road or mountain bike class. They are a USA icon but now, like most bikes, are made in China or Taiwan.
Honda
Basically the same as road bikes, but with thicker tubes and bigger welds.
Most mountain bikes are made from Aluminum, some are made from carbon fiber and older bikes are made from steel. Quality, weight and strength vary hugely by manufacturer with most high end bikes claiming unique methods which either reduce weight, improve strength or both.
Yeti bikes are sturdy bikes that are manufactured for mountain riding. They are made with stronger parts and brakes that can withstand the rugged terrain.
bmx's are made for trick and stunts and only have one gear & they don't have suspention they are also smaller , mountain bikes are more for terrain because they have gears and suspention and are a bigger
Mountain bike frames are made from a variety of different metals. Some sturdy frames are made from titanium alloys, while others are made from steel. Lightweight mountain bikes may also be made from aluminum.
The best inner tubes for mountain bikes are typically made of butyl rubber for durability and puncture resistance. You can purchase them at bike shops, sporting goods stores, or online retailers like Amazon or REI.
A mountain bike is the bicycle equivalent of a SUV or a Jeep, it's a bicycle made to go off-road.
Your question is too broad. There are many American manufacturers. Some specialize in BMX bikes, some mountain bikes and some road bikes.
For better traction. Street bikes are made to ride on concrete and tarmac. Pretty much the same terrain everywhere. Mountain bikes are made to ride on dirt, mud, gravel, sticks, rocks, grass - and to get traction on those types of surfaces you need a wider, knobblier tire.
stingrays are made of cartilage like from our ear arent they?