Sub Or Function

I know the basic difference between a subroutine and a function is a
subroutine performs a task and a function performs a task and returns a
value. The Call keyword is required when using parens with subs with more
than 1 parameters. Parens around values passed are ByVal vs ByRef and is a
waste of processing if passed ByRef for no reason.
I am told there is no reason to ever use a subroutine as a function can be
used even if it doesn't return a value. While this appears to be true, is
there any reason why it's ever a bad idea to use a function, instead of a
subroutine, that doesn't return a value? Are there memory, performance,
etc. issues?