Here is a conceptual reason why without math using extremes.
First some statements, then the actual reasoning:
There are no completely isolated systems in the universe, and every system loses a positive amount of energy as heat into the environment. Heat flows from hotter to colder, and there are always colder regions out there until the universe reaches thermal equilibrium (ignoring fluctuations), which won't happen for trillions of years. The entropy of a thermally insulated system cannot decrease and is constant if and only if all processes are reversible. Because there are no perfectly thermally insulated systems, you see the flow of heat and thus increase of entropy in the universe. But reversible systems allow for the backwards flow of heat and entropy, so we need to establish at least one irreversible process. Once we have it, the above all comes together to give the entropic arrow of time, and thus we can say every process or system loses energy to the universe as whole. So you need to input energy to a system to keep it equilibrium (with itself, not the environment).
As far as irreversible processes. This is a very interesting topic, and I have asked questions on SE before for clarification. Until I get a response, I will appeal to Susskind's belief that there are no irreversible processes without the multiverse. Even in an accelerating, expanding universe like ours, we still have reccurances due to the finiteness of our "box"/horizon. This guarantees a backwards arrow of time at some far future point. So we wouldn't have true, complete irreversibility. Enter Susskind's argument that Koleman-De Luccia processes of bubble universes forming and collapsing within eternal inflation produce a truly complete irrervisbile process. My understanding of his reasoning is that the rate of universes being spawned is so great in such a multiverse, it out paces the number of universes currently in recurrances, which is why we can use self-sampling to say why we don't see any recurrances in our universe. Susskind calls this process a fractal flow. The total makeup of the multiverse is thus trending toward more and more fresh (and thus not in reccurance yet) compared to the aging ones. The multiverse trending toward this is the ultimately the arrow of time, and ultimately the irreversible process needed to completely explain why we witness only a singular direction of time - and a roundabout way of answering your question.