A Tablet is great for using to read e-books, watching videos, playing games, and other activities, but it is not very good because it lacks a physical keyboard, and the onscreen touch screen keyboard can be hard to use, and slippery.
There are companies like Logitech Tablet Keyboard for Android 3.0+ (Keyboard-and-Stand Combo) which make USB or Bluetooth based keyboards for you to input text on your tablet with a keyboard similar to your laptop's or PC's keyboard with all the letter, numbers, directional and other keys.
This will make typing long e-mails, documents, and doing office work on your Tablet a lot easier then using your fingers and the on screen keyboard since a keyboard is easiest to use to input text into your tablet PC because you can use both hands to type on the keyboard rather then peking each individual key on the onscreen keyboard on a tablet. Using both hands to type on a keyboard will increase your productivity since you can now type text twice as fast on your tablet with a keyboard.
Using a keyboard to type text on a tablet also reduces the number of fingerprints or scratches on the screen since you touch the screen less since you are no longer using the screen to type, so it reduces the chance of you scratching, and smudging the screen with your fingers. Your touch screen will last longer because you are using it less to type, so there is less wear and tear from regular use from typing on the on screen keyboard.
Plus, you can also move your tablet PC farther away if you prefer your tablet to be farther from you when you type. Having a keyboard also frees up your hands for typing and viewing videos since most tablet pc keyboards also come with a stand or a case for you to hold your tablet on to hold it while you watch a video.