Ezra Pound reduced "In a Station of the Metro" from 30 lines to two because he wanted to make the poem more concise and direct.
Pound originally wrote a 30 line poem about his experience in a Paris metro station. However, he threw this version in the trash because he didn't like it. Later he tried writing a shorter poem, but it also ended up in the trash. After reading Japanese haikus, he was inspired to write the two-lined version. It is now one of the most read poems, mostly because it is so short.