Hashtags were first used in twitter as a way to categorize the content and making it more browsable by the users.

If two people used the same hashtag you could see both of the tweets (given that you clicked on the hashtags itself).

Facebook also started using hashtags for the same reason, but given the different type of user I see that many people uses hashtags to condensate a concept or a catchphrase.

So, basically they reduce the power of their words by reducing the content.
You don’t express the full range of emotion through words, but you express it through simple messages, way smaller the what you’re feeling.

It’s up to you to decide how to express yourself in your life. When in november I did a trip to japan everyday I would post a photo with a long description of what I liked and what made me astonished (in a good way).
People loved it, because it allowed them to live a small moment of my life, to see with my eyes.
It was nice, and I felt like a small japan-guide 😀

It’s easy to shorten words, to use them less, to use tags.
But we’re humans. And although it’s funny when we use these new tools, we always receive and live more when we are back to our roots.