Yeah, Playwright is perfectly suitable for API testing as well, and I even compared it against Jest https://javascript.plainenglish.io/api-testing-comparison-cypress-vs-playwright-vs-jest-2ff1f80c5a7b

But sometimes, you don't need to do UI testing or have HTML reports — when your project is only a backend application on Node.js, or when you want to migrate your API tests from Jest to something fast and modern (in the case of Playwright you'll have to rewrite autotests, while in Vitest you can almost only switch a tests runner).