We talked about why you should invest in a 50mm lens. Now let's talk about why you should be investing in lenses in general. 

Camera bodies come and go--Quite frequently. New models are always coming out, with newer and better technology each time. Especially with competitors trying to out-do each other.
Buy a top of the line DSLR and in one to two years, a new camera will come out that you'll wish you had, instead of the one you already invested thousands of dollars into. It's just how the market works.
All the more, with the entry level DSLRs, there is always going to be something new coming out. And not just that, they'll always be a better camera model more advanced and capable than the one you have.

So, when you're starting out. Do not focus on that. Stick with whatever basic DSLR is it that you're shooting with. And start investing in better lenses.

Lenses hold their value in a truly fantastic way. Especially when they are taken care of. They aren't updated near as frequently, and even when they are, the older lens is still relatively valuable. So it's a better financial investment.  And even more importantly, better lenses make for better pictures.

I shot my first wedding with a Nikon D3000. Which in retrospect was said to be one of the least desirable DSLRs that Nikon has produced. Not only did I shoot my first wedding with that camera, but I started my business with it, and earned enough money to buy the equipment that I have today.
However, I got away with this because of my lenses.
I was blessed to be able to buy a used 70-200mm f/2.8 from another photographer, and it changed my photography overnight.

On a quick side note--My photography was ready to take the next step, because I had been working for quite some time with the basic equipment I had, and I really learned how to utilize it to the fullest. I am a much better photographer today for this. If I had started out with the equipment I have today, I would not have learned near as much. So while you're saving up for the nicer lenses--Don't feel bad about what you are shooting with. Take it a crucial step in the learning process.

Here are two senior photos taken within about a month of each other. Same camera, different lens.
The first I took with the 18-55mm f/3.5-5.6, the second is with the 70-200mm I mentioned before.

The first one isn't a bad picture--Like I said, I had really learned to utilize my equipment. So it's absolutely possible to take good pictures with the cheap, kit lens.

But the second picture is just wonderful. Really fantastic depth of field, creamy, blurred out background, beautiful bokeh. Yet such a sharp and clear focus.