It is easy to remember short domains, they are quickly typed in and fit perfect for short and easy to remember e-mail addresses. They are perfect for advertising purposes, e.g. car branding, placard advertising or ribbon advertising. The shortness of the domain name also helps in general design of a website or company logo. In the ideal case the domain name is similar or same to the official name of the company (bmw.eu) or matches the product being sold (app.eu).
There are also many abbreviations, which are described exactly by short domains (e.g. pga = professional golf association). Fact is that there is a maximum of 676 two letter and 17.576 three letter .eu domains - due to the total amount of letters. Not only because of this reasons short .eu domains, which consist of a pure letter combination are special valuable.