Why Catch a exception in asp.net if customError=On

Hi.
I have a question, 
On my site I have the customerror to on(it will be chagned to remoteonly later) in my web.config so I can show user friendly error sites and also log the errors.

But everywhere i read about doing this everyone says that it is good to use try...catch blocks in ur code to handle all errors, so defaultRedirect in web.config is only for unhandled exceptions.

But why cant u let all Exception on ur asp.net site be unhandled and let the server redirect always to the defaultRedirect error site? wouldn't that be easier instead of using try....catch the in the code where u know there might be an error?

Armen
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