Earlier quoted context omitted.
It actually works a bit differently; it's not all scraping. People enter data into Zenefits and then it populates that data into ADP. I don't think the issue is as cut and dried as the typical web scraping situation and I wonder how HN readers feel about this kind of thing. The data belongs to the client. The client chooses to use both services. Should it matter how the client accesses their own information from the…
Generally, from an ethical perspective, it matters at the point when you choose to build a business on the method of accessing a 3rd party service. From a legal perspective, the profit-making purpose is irrelevant. Improper access matters when you start using the service.
Why? They are having to pay them and then buy your services for data entry. This is no more unethical than hiring someone to do your banking for you.
Violating an EULA by doing this may be unethical, but in that case, it is violating the EULA that is unethical, not the general practice of providing a new interface.