Existing symbols in the libraries can be utilised in new components. In fact, this is a key concept of our libraries.
If you have a series of resistors, why have a new symbol and footprint for each one when they all use the same shapes? Just re-use the same two symbols as many times as you like. The only time you may need to change a symbol is when the footprint pitch changes or when you use a surface mount variant instead.
As well as speeding up the original creation of new components, this can also help in rapid updating if you find a problem with a symbol. If all your resistors use the same 0805 footprint and you find a problem with one, correcting and reloading that footprint will put right all the components that use that footprint.