With the premise of the uselessness of genres/labels and their very existence, I can tell you that what is called "Ambient" is nothing but another way of expressing ourselves through sound design and the art of crafting soundscapes. Said sonic worlds can be ignored, but once you start paying attention to them, you realize how the timbral and atmospheric aspects of a well-layered composition is able to hook you up and drag into a state of relaxation, self-discovery, or meditation. Just like any other style, it's purely subjective and pretty much love it or hate it. That's up to you if you enjoy the slowness or even rhythm-less of some tracks.
Personally, it's a style that helps me cope with the absurdity of the world we live in. It's some sort of mind training for me. The more I compose such "healing" pieces, the more I feel satisfied with what I have achieved with my own strengths, and the more I can relate myself to that shard of imagination. You'd be surprised how much some tracks can be so deep to resemble dreams - dreams that anybody can relate themselves to.
Ambient is also an experiment, it's an ever-growing movement. It draws active influences from various styles and it is thus unpredictable. It can be funny, ironic, sometimes sarcastic... Everyone can make "Ambient" by just copy/pasting a pair of notes for 30 minutes and then try to sell stuff online (and believe me, "spambient" makes up at least 80% of the Ambient market, which is already limited by itself). The trick is about giving depth to the track, you mustn't force yourself to make something you can hardly grasp. Be creative, let your mind guide you in a journey that will allow you to unlock the doors to a grander, vast sonic reality.
My personal favorite artists are Solar Fields, Carbon Based Lifeforms and to some degree even the pioneers of Ambient music, including Brian Eno and his "Ambient" series.
It's a funny aspect of music to explore. Somebody could even challenge the very definition of music, by making abstract compositions that seem to defy any common sense, so to speak. In fact, I don't think it's about "making sense", rather... "feeling" what you're listening or making. Trust me, I find this approach to be the most efficient and useful.
Hope I've been of help. :)