Using 3rd party/off-the shelf stuff is simply a fact of life in development. Even if you have the expertise to write everything from scratch, the tradeoff in development time/cost usually isn't worth it. Trying to do it for multiple platforms is even more difficult. There's also the personnel factor. If the person who wrote the custom code disappears, someonne else has to try to figure it out - often a daunting task. Finding someone who is familiar with the 3rd party components is probably going to be easier. For some of same reasons that few people bake cakes from scratch these days, few people are going to roll their own media player etc. to put in an application unless their needs are pretty unique. The downside is that you're always vulnerable to changes in the outside components/frameworks etc. you're using. Even the code you write yourself is still subject to changes/patches to the operating system. Short of writing everything in machine code, I don't see a way around some level of dependency - and even then, you have to hope that Intel doesn't screw you :-)

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken