Authentication required everytime signing into my account? WHY?

[R4074]

Why is it that every single time I sign in to access my verizon account on my computer I have to receive and respond to not only one text, but 2? 

If I am a spammer I can easily mimic a fake VZ number and call on subscriber pretending the be local  but if you are an actual subscriber and want to do something like pay your bill they have to do multiple security verifications.   It is a complete hassle and why 2.  If I have my phone the first time why is another verification required to go to the next screen.