It does defeat the purpose. The iPad is designed to be a portable device that you can take anywhere and everywhere. If you're just going to use it at home you might as well use a laptop.
A laptop is a portable device.
A desktop is designed to be used at home.
If a laptop is portable, and designed to be moved around, taken to work and back, and so on, then does it 'defeat the purpose' of having one if its used in the home only?? I know a very large number of people who would beg to differ, and use their laptops at home only - just because its more convenient, and its down to HOW its used.
The same with the iPad. Young kids find it easy to pick up and play games on over a laptop - my main reason for purchase. Others will only use it at a certain location. Just because its not carried around it doesnt mean its not being fully utilised. It all depends on your own individual needs.
In your case maybe Apple should market it as being an out and about device only, and state its not suitable for home use only then??
Every device on sale today, be it a laptop, desktop, phone, whatever it is, is purchased by people to fill a particular need. As long as it does what you need it to do, then I dont see how it defeats the purpose of having one.
Maybe everyone should start to use their equipment exactly as you use your then? Since if they dont, they arent using it the right way?!
Oh and let me know how you hold your iPad as well - I want to make sure I'm holding it like Im supposed to?
As I said, as long as something you purchase fits your own personal requirements, then its doing what was intended.