I'm going to show you three photographs, to illustrate a point.
I take most of my photos with a prosumer DSLR; which is jargon for a Digital Single Lense Reflex camera, that's one step below what pros use. IN particular, I have a Nikon D80, which is actually one of the more popular backup camera choices for a lot of professional photographers.
It's a spectacualr camera; but It's also about a thousand dollars, and being an SLR, it's fairly large. In these days of every cellphone being a camera... in fact up to a 6 megapixel camera in some cases (which is meaningless, or even harmful considering the size of the things, but that's another post), and teeny tiny little 10 megapixel point and shoots, I've been asked (many times in fact) "why bother".
It comes down to options, and control. POint and shoots are jsut fine is your subject is sitting still, in decent lighting, etc... ; and honestly thats what most people will use them for, most of the time, so most people will be happy with them most of the time.
But what if you want to shoot a subject that moving fast? Or in odd lighting conditions, or with a complicated background you want to fuzz out... or really any number of other situations or effects you may want to create. Frankly, even in the best point and shoots, you jsut can't do a lot of that.
Let me illustrate my point with those three photos I mentioned. The first is a photo from my pro-sumer camera, which certainly has a better sensor, and better optics than any point and shoot you're likely to find; when it's set in fully automatic point and shoot type mode:
These are completely unedited except to reduce their size by the way.
In this photgraph, you can see what the room would look like to non dark adjusted eyes coming in from a bright space; which is typical of point and shoot performance.
The room is actually about 28x16 foot, with white walls and ceiling, and bookshelves and seating lining the walls. The only lighting in the scene is from the blue LED on my stereo, and a couple of other small LEDs; plus some reflected light from the door crack of another room down the hall. Certainly there was less than 1 lux illumination across the scene. I was barely able to distinguish the camera at arms length.
This second picture is my camera in it's special fully auto night/dark mode; which emulates a faster film speed, and uses a slower shutter speed and faster aperature:
In that picture, you can start to see some detail, though not much. Again, clearly color vision isn't possible. This is about what my eyes adjusted to after a minute or two.
This is about the best you're ever going to get with any kind of automatic exposure, shutter, focus, and film speed controls... and frankly, there's no photo there; just a little blue blurriness.
Now, take a look at what you get when you use full manual controls, and the maximum capabilities of a pro-sumer grade camera:
You can see the scene now. In fact, were the LED not blue, you'd have full color vision. Before I reduced the size, I was actually able to read some of the book titles.
Remember, these three pictures are the same scene, and same lighting. The only difference is the level of control over the exposure controls within the camera to take advantage of what light was available.
That scene was a 30 second exposure at f3.6, exp+5, iso 3200 (which is why it's so noisy/grainy). Both of the other photos only used about a 4 second shutter speed, and ISO 1600.
You just can't do that (or at least not easily, or well, or without unacceptable levels of noise) with even the best point and shoots. And of course you can't take a huge variety of shots that better equipment makes not only possible, but even easy.
I'm going camping up in the mountains of Northern Arizona this weekend, and if the sky is clear and the moon not TOO bright, I'll take some starshots to show you guys.