All mics colour the sound in different ways. For some reason the U87 adds a colouration that's perceived as expensive, larger than life, and authoritative.
Other mics - including cheaper Neumanns - don't have quite the same effect.
It's not about capturing the sound perfectly accurately, but about creating an impression with sound. That's why some pro audio gear is so insanely expensive.
It's very hard to create the same impression digitally because this kind of subtle analog distortion is complex, non-linear, and not very well understood.