It might seem like a lazy design decision, but including a crown in a logo design can be an effective way to communicate luxury, wealth, legitimacy and superior quality. Crowns are easily recognisable and fairly universal, with many cultures around the world being familiar with some form of headdress as a status symbol. It's also a clean, solid symbol that can be easily rendered in an abstract form for use in small sizes.
Finally, crowns are now so widely seen that they've lost their exclusive connection with royalty, so it doesn't necessarily come across as pretentious for a small brand with no royal connections to use one – even graffiti artists use crowns in their tags. It can be seen as arrogant or conceited, but with the right brand, a crown can communicate tradition and permanence.