Purpose of the model - less then in CI3?

Sorry if this is a stupid question, but do we generally do less stuff in the model now compared to CI3?
For example would I do the sanitazion of  "Post data" in the controller now and not in the model?

PHP Code:

$data['fieldname'] = $this->request->getVar('fieldname', FILTER_SANITIZE_STRING);
$model->insert($data); 


Why do you need to do the sanitization of "Post data" in the model?

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Why do you need to do the sanitization of  "Post data" in the model?

Well,.. I don't have to, but I used to do all the data modelling in the Model with CI3. 
So, I understand your feedback as a confirmation to do that in the controller. Thanks!