Approximately 90% of people are right-handed. In European writing systems that use quills and pens, reading and writing left-to-right makes more sense so that you can hold the pen in your right hand and drag it rightward, not into the ink you just laid down.

In East Asia, before writing on paper was a thing, they wrote using inscribed bone, but then eventually moved to vertical wood boards, bound together by string. Each character on the board would be ready from top-to-bottom, and then move to the next board. The most logical choice for a right handed person is to stack the wood pile on their left, and use their right hand to draw the next board to meet their gaze, then set it down on their right. Later, this bundle of wood boards would become paper scrolls, but would still be pulled from left-to-right by a right-handed scholar.

For this reason, the historical writing system common to China, Japan, Korea, and Vietnam for centuries was read right-to-left (because instead of scrolls, we have pages, which can be moved easily). But the native Korean script is left-to-right, as is the modern Vietnamese script. And Chinese and Japanese in the 20th Century switched to left-to-right. And yet, Japanese books are still ordered “backwards” so that the title page is what Westerners would say is the back of the book, and manga panels are read from the right side toward the left.

So far as I’m aware, this means some Japanese signs can be rendered left-to-right (modern), right-to-left (historical standard), and top-to-bottom (traditional). The only orientation that’s disallowed is bottom-to-top (although vertical news tickers will do this, so that readers see the text from top-to-bottom).

It all boils down to right handedness, but it depends on whether your hand is moving, or the text is moving.