It's not just the number of applicants which is of some interest to HR and finance. It's also the profile of said applicants. As long as a given offer attracts a sufficient pool of experienced candidates, what's the incentive to try and offer anything better?
Which, IMHO, is a little bit pointless these days because no matter what you offer, there will be someone desperate enough to sign up for it. In at least 2 years from now the "survey job advert" tactic might give some meaningful answer to the question how low can T&Cs go while still attracting decent people; this year or next year It's a downright waste of time because so many people will happily go for anything out there, even if it involves moving to a war zone on half of their previous salaries.