It's really useful for small businesses that want to accept credit cards without having to get a full-blown merchant account. If your business is really tiny (

It's really useful for small businesses that want to accept credit cards without having to get a full-blown merchant account. If your business is really tiny (like a little side project) and makes less than, say, $100k/year, a merchant account can be too expensive, plus setting up your website for the merchant account is much more difficult than PayPal integration, which is almost trivial (the simplest form is to just add some HTML buttons to your site).