Is there any reason to disable paste password on login?

Today I logged in to pay my cellphone bill, and I found that the site has disabled paste functionality in password field.

I'm a webdev and I know how to fix this, but for regular user is REALLY annoying having to type a random password like o\&$t~0WE'kL.

I know that is normal to make users write the password when creating an account, but is there any reason to disable pasting passwords?