Psychology as a hacker's weapon

Today, students discussed topics for graduation projects. I was asked if I could legally “get” passwords and logins? In general, the idea was born to make a simple service, let's call it for example “compliance”. The idea is simple - beautiful design, domain and title: “Check if your login matches your password!” And there are two forms to enter: Login and Password. And that's all. Next, a simple script for generating results (all honestly, after all) and a more complicated script for pulling information about a person who came. And then a simple search by login - and voila, we legally get access to a bunch of sites and other things. There was only one question - how many people will enter their "standard" set of login and password?