Here's a quote on simplicity from Albert Einstein:
Everything should be made as simple as possible, but not simpler.
That quote sums up why making things simple can be difficult.
Less source code is better. This is almost always true. The exceptions to this are so rare that every time you think you've found one you should REALLY doubt yourself. Less lines of source code almost always means less code that new programmers have to understand when they come on the project. It means less stuff for you to remember next year when you are in the middle of another version. It means fewer places for you to have mistyped something. It means fewer instructions to execute. It means fewer things to change when you re-architect.