Hey there!
The most common belief for why he did this was to promote originality. Most poets in that time used rhyming meters, and they still do today. In fact, you were probably taught rhyming meters in school - they follow rhythm and pattern that isn't subject to change.
Robert Frost wanted to break the rules. Considering the nonexistent popularity of the style he intended to use, he created an entire new type of poetry and writing by breaking the rules themselves. There was no rhyme, but there certainly was reason.
Hope this helps!
