Why does the align environment right-align by default?

Question

If you use the align environment without any & characters, it right-aligns your equations. Who ever right-aligns equations?

Answer 1

If you use an align or align* environment and don't provide one or more & markers for each and every row, you're probably misusing the environment. (If you want to center the rows, use a gather or gather* environment.) Don't expect the software to bail you out and somehow intuit -- correctly, no less... -- where the alignment points are supposed to go.

Right-aligning the rows that are lacking & characters, then, is align's way of delivering a powerful and difficult-to-ignore visual message -- the equivalent of "Uh oh, I think you've messed up." Much more powerful, for sure, than issuing a warning message -- which many (most?) users tend to ignore anyway, right? Of course, if for some reason a user does want to right-align the row(s), then that's what he/she gets -- without being bombarded with patronizing warning messages.

The upshot: If you do not provide & alignment markers in each and every row of an align or align* environment, you should almost certainly not be using this environment to begin with.