Some people eat alone by choice. Some don’t. Noticing and never asking is still a choice.

Sitting alone is sometimes a preference and sometimes the only option available, and from across a room the two look identical. Deciding not to ask is itself a decision, even when it feels like neutrality. Nobody is obliged to fix anybody, though noticing and then looking away is not quite the same as having done nothing.

You can ask without turning it into a project. Sit down, say hello, or invite them once and let the answer be whatever it is. If they would rather be alone you have cost them nothing, and if they would not, you may have changed their week.