python isn’t the only language to do “execute everything imported from a particular file and all top level statements get run”. both node and c# (but with restrictions on where top level statements can be) can do that type of thing, I’m sure there’s more.

python conventions are unique because they attempt to make their entrypoint also importable itself without side effects. almost no one needs to do that, and I imagine the convention leaked out from the few people that did since it doesn’t hurt either.

for instance in node this is the equivalent, even though I’ve never seen someone try before:

if (path.resolve(url.fileURLToPath(import.meta.url)).includes(path.resolve(process.argv[1])))
{
  // main things
}