Even in smaller applications this is incredibly relevant.

I've recently written something that's meant to interface on a local area network, just controlling something on another computer, literally just one or two users at a time -- thing is the precision of floating points are a big thing here, and we have to consider that. So all of the bignum stuff had to stay server-side in C++ after much messing around doing math client side in javascript only to learn the hard way how completely broken that is. Fun fact - You can't maintain state when floats start to drift off of values they were supposed to land on due to javascript's crappy math libs