In general each export is named with what it is, so SearchWidget.tsx, which contains a search widget, would explicitly "export { SearchWidget }".
Both tslint and eslint support no-default-export rules, so its clearly at least a semi common approach.
I can't speak to why others use the pattern but I can say enabling no-default-export gets rid of the "do I import * as foo from, import foo from, or import { foo } from" conundrum and enables the linter or transpiler to detect when there is code that accidentally tries to import Football from "baseball" because import { Football } from "baseball" (when baseball.tsx doesn't export Football) generates a clearer and more targeted error message than some noise message about invalid props or wrong number of children under <Football> because it picked up some bogus default export from baseball.tsx. (Definitely not trying to start a language war here, engineering is always about trade offs, and different people and projects make them differently without invalidating each other's choices.)
I'm guessing there is a way to make a generic transformer but it's not a type of TypeScript language fu I've messed with.
