Why is the User verification required?

Question

I am very curious to know some of the points regarding registration and login related points as a developer points of view. Please see below the steps for any online account which is publicly open for all,

1. CREATE USER ACCOUNT : Insert the data entered by user along with a column activate which default value is 0

2. SEND A LINK TO ACTIVATE : a link has been sent to user email at the time of registration

3. ACTIVATE THE ACCOUNT : user clicks over the link and the link is verified and update the column 'activate' with value 1

Why to sent a link & verifying is necessary which I supposed that is not utmost required. I asked to clients why u want such verification and i get the answer almost same e.g. checking the authenticity of the user and it'd be helpful to stop the duplicity of the user. but practically at the time of user login, i suppose it is useless to verify each time the activate column along with password for every user.
I would appreciate if u explain the points which is very important regarding my concern.

Answer 1

This is really a slippery slope, but there are reasons. Obviously spam users will try to create accounts as quickly as possible, for spam reasons. Email and captcha verification will handle this.

Another is the issue of clumsy or accident-prone users that will forget their passwords, which can be worked around by email reminders/resets. Sadly, users may try to add fake email addresses(or mistyped ones) and lose access to their accounts, requiring admin intervention. Simple verification can force users to get their account into a self-rescuable state before adding any data.