Why do people need pets?

Why do people need pets? This is a good question. Today a great number of families have pets. Some are dogs, some are cats, and some are fishes…
There are many reasons. The biggest reason is pets are the our best friends besides the humans. Especially the animals like dogs and cats.
Let’s go back to the earliest “pets” in our life.
In the past, people didn't have machines. So people needed to do many things with animals, like the Alaskan Malamute.
Later, we didn't need to do things with animals anymore, but we continued the habit of feeding the animals.
And I watched some movies about pets. The Most of them are dogs and cats. And they are really close to people. But some people keep some weird pets. Like Arrow-Poison frogs, spiders, and monkeys…
So I researched about this on Internet, the reason of people keep the weird pets is the people who feed them are alone and they want to find some things like them (I'm not sure what exactly you mean here - do you mean to say something like "they want to have a pet that is similar to them"?). And another reason is they want to be cooler.
So I think these are the reasons of why do people need pets.

Nice text! One way to expand your vocabulary would be to use specific words in place of "do things".