From a Jerome Bigge on lunar observer egroups:

1. You can see a lot of stuff even with just
a 50mm refractor... Or even 15x70 binoculars.

2. The view of it changes from night to night.
The way the sun hits it changes, causing a
change in the appearance of craters and
ray formations.

3. Men have gone there and walked on it.

4. It's around a lot at night. All year long.

5. Even in the worst light pollution you
can imagine, you can look at the Moon.

6. Most people start with the Moon. I
think of it as an old friend who is always
there... I started at the age of 8.

7. You can get good photos of it with
even a relatively cheap digital camera.
I have one on my web page that was
taken with a 50mm refractor and a
Canon A10 digital camera.

8. It is much more impressive in a small
scope for non-observers than anything else.
(Mars is a big disappointment for most)

Jerome Bigge

I'd add:
9) It is extremely different from Earth and yet at the same distance from the Sun, so, scientifically worth it.

10) A personal relationship (just by looking at it, for instance) can be built because it's much more to our eyes than just a point of light.
(Jupiter is a little disk to my 20x80 but those binoculars are not that easy to carry around).

And that's only from an amateur astronomer's point of view.

Raoul