There are lots of very good reasons why someone may wish to make their own apps for your iPhone, for android phones, and any other smart phone as an example. If you are an entrepreneur then there is loads of money to make from this, either by creating excellent premium apps that you can sell, or creating free apps which include some kind of advertising within them. When you have your own business, and much more particularly if you have your own website to promote, then creating your own phone applications could be a great way to either generate extra money, increase the loyalty of one's customers / visitors and have them coming back to you on a regular basis, or to make your content available through a new avenue. Apps are big business now and there really is no reason to let yourself get left behind.
And also if you aren't interested in the business enterprise side of things you may well get yourself a lot of pleasure from playing around and being creative - making your personal applications and bringing your thinking to life so that you can share them with friends and family and perhaps other folks too.
And although many people probably think that you have to spend a small, or even a large fortune to create something like this, which may not be the case. You'll find places that you can go which you could make something totally free. Widgetbox.com have a good program, as do appmakerstore.com and others too. Simply do a Google search for free app builder or something similar.
When choosing which one to use, or if they are right for you, the main thing you need to think about is what kind of functionality you want to have. Generally advanced things using the GPS or just being able to perform custom functions by shaking the handset will require you to spend a minimum of some money to get a professional to do some programming work for you. The free tools that exist will work from set features which you add from the menu and then fill in the forms and so on with your own details and content. Use this to add feeds from the blog or twitter account, create a guide or a quiz, create different pages with text, images or videos, and also other things like that.
It really is surprising what you can do for free - although you may need to upgrade with a few services if you get a lot of users - therefore it is well work looking at if you have an idea with an app or a website or business to market.