Most shrubs do not actually 'need' pruning! (Now that's a pretty good way to start on pruning: I will now bid you farewell and let you get on with it!)

But; many shrubs are planted in the wrong situation - in relation to size and position, so pruning becomes necessary. Add to that, the fact that we are usually more concerned with having the maximum amount of flower/foliage/stem growth, than we are with the shrub's feelings, then the need for us to prune our shrubs over-rides the desire of our shrubs to be pruned!It is interesting to note what happens after the pruning of a shrub...... 

If you prune  a shrub down to - or near to ground level, it will send up vigorous growth to the same height (normally) during a single growing season! When you want long 'canes' of new growth - as in the case of some Cornus (Dogwoods) - this is great. (On the other hand, if you are a bit of a 'snipper' at the ends of twigs, then you will end up with rather weak insignificant growth - similar to that which you have 'nibbled at'.)

All of that having been said, it is also true that young vigorous growth, is more likely to have more prolific flowers and foliage (and stem colour) than older growth. (A bit like us humans really I suppose!)