Thousands of reason for this but not everythings worth mentioning. Yeah. Who would carry a metal stick around anyways? It's heavy and total burden for us. But that doesn't mean its useless.
You think still pictures doesn't need a tripod (or monopod)? Think again. The pros always carry these stuff around and that's why their photos cost more than you ever think of. Even if your camera has super-great image stabilization, your hands and camera shutter will still disrupt that. Stability is what the pros are after besides the quality. Even in the wild savannah or the metropolitan, tripod is useful. In a certain way the pros see it. How about the amateurs? Well. Up to you I guess.
Low light photography or fireworks shooting will require long exposure and I bet your hands will not be enough. Can you stand still with your camera for 30 seconds? Even guys with muscles will have a hard time. Gravity makes it difficult and thats where the tripod comes from. Macro shooting will require it even more. Not just that, sometimes you need to be in the picture and the metal tripod will definitely do this dirty work right?
It is more tiring than photography. The equipment is just too heavy. With still photos, the most you need to hold on is for a couple of seconds. But not videos. A minute will always feel like forever. Seriously. You need to be still because shaky videos is a cheap videos. Believe me. Even a small tripod will do the job as long as it can support the weight of your equipment.
What do you need?
Okay. There are several types of tripod. The normal ones you will find at the roadside is called a tripod made of aluminium. Its cheap, easy to carry around and can't support heavyweight equipment. The other tripod made of solid steel or anything metal, will work the same but it can support more weight and some, up to 10kg. The feet is usually made of rubber for better grip. And 3 section feet will allow you to adjust according to your liking.
Another one is called a minipod. From the name, its small. Usually for people who like to take their own picts. One of the minipod that is very popular is the gorillapod which is very versatile and flexible. You can attach your camera to your bike, hand, leg and even car steering. Isn't that fun?
The monopod is the one you will see at sporting events. Why? Everything is so fast, setting up a normal tripod would take too much time, thus a monopod was born.
That's it for now. Hope that'll help in your life. Thanks for reading.