This is fairly easy. A period marks the end of a sentence. It is a lovely thing to offer your readers. The period will let people know where one thought ends, and another begins. Traditionally it is followed by a capital letter to further clarify one's meaning.
Things can get confusing without a period if you don't use a period then I can't tell where one thought ends and another begins things just run together we can avoid this by simply using the most basic punctuation mark my words it will increase comprehension of your writing
If you don't use periods I will most likely give up and move on to something easier to read. My time is valuable and there are many things vying for my attention, whether it is on a blog, Facebook or anywhere else. I have friends whose status updates, stories and other written items I refuse to read because it is just too much work to decipher them.
And I am not alone.