Why do you need to encode URLs?

Question

Why do you need to encode urls? Is there a good reason why you have to change every space in the GET data to %20?

Answer 1

From RFC 2936, section 2.4.3:

The space character is excluded because significant spaces may disappear and insignificant spaces may be introduced when URI are transcribed or typeset or subjected to the treatment of word- processing programs. Whitespace is also used to delimit URI in many contexts.