One more thing,

in Europe it is vastly more accepted to have a OMB at a wedding or special occasion than a band, even though you'll see that too.
But you do expect a hell of a lot from them: playing the latest music of the pop charts, telling jokes and doing animation/games with the audience, especially at a wedding.

Bands perform more in large clubs, more as a concert kind of venue.

I guess different things are expected from musicians in Europe vs the US.

Eric