Webdynpro MVC Architecture

Hi,

I have this q in mind for a long time and even after surfing a lot, am unable to get the proper answer.

According to MVC model we need to have the business logic seperately in a model.

can anyone pls explain me why the performance will be affected if I put a select query in view hook methods or some where directly without a model ( FM or class methos) .

Thanks

Nags.