Take a look at your computer's keyboard - Ain't that a mess? Normal would be for the letters to be in a line, like A-B-C-D and not Q-W-E-R-T-Y...
As a matter of fact, this type of keyboard layout is called Qwerty because of the 5 first letters. This layout was developed in the early 70s by a newspaper editor and printer from Milwaukee, Christopher Latham Sholes, and his friends, Carlos Glidden and Samuel W. Soul. Until then the keyboard had a more logical layout:
- 3 5 7 9 N O P Q R S T U V W X Y Z
2 4 6 8 . A B C D E F G H I J K L M
But the mechanical typewriters that existed back then had a major flaw: They jammed when two nearby buttons were pressed within a short interval. This could cause a headache to experienced typewriters who were already able to type many letters per minute. The Qwerty keyboard was then introduced to solve this problem. Commonly paired letters like s-t, t-h, p-r etc were placed apart from each other so that their typebars were not neighboring avoiding jams.
Check out your keyboard once again. Every word in the English language has at least one vowel. But the fingers home-row (the middle one) has only one vowel, that is the letter "A". This means that the fingers have to leave the home row very often slowing down the typing speed. Nowadays this feature indeed slows down the typing speed, but during the mechanical typewriter era, it was meant to speed up typing by reducing jams.