Our eyes have been trained to do this since the printing press, and it's just a typographical standard to left justify any block of text that requires more than a few seconds to read. It's generally easier on the eyes and makes it a lot easier/quicker to digest information.
What do you call text that is aligned left *?
justified—text is aligned along the left margin, with letter-spacing and word-spacing adjusted so that the text falls flush with both margins, also known as fully justified or full justification; centered—text is aligned to neither the left nor right margin; there is an even gap on each side of each line.
What does left-aligned mean?
For example, in a paragraph that is left-aligned (the most common alignment), the left edge of the paragraph is flush with the left margin. Vertical alignment determines the position of the text within a section of a document relative to the top and bottom margins, and is often used to create a cover page.