So, yes, it's hard to build. That doesn't mean that no one can do it. Many companies have done so, including several startups. And, given how poorly one of the market leaders (Intuit) has implemented it, I'm willing to give a startup a try.
Not entirely, no. There's a history of Zenefits customers and their employees suffering from serious technical and support failures.
http://www.buzzfeed.com/williamalden/zenefits-hr-rocket-ship...
>in late February this year, with coverage supposed to start days later, Zenefits informed Hawkins that it had made a significant mistake, attempting to enroll his employees with an insurance provider that didn’t cover the company’s region. The insurance wouldn’t come through as planned. [...] In several cases employees like Harris, who had put their trust in Zenefits, were left without health insurance for a month or more after they had expected it.
Not an ADP user I presume.
I wish a payroll startup would put resources into a nice UI and having some really season support too. Just doesn't seem to be there yet, unfortunately.
There is zero chance I'd subject employees to a hacked together payroll system. Building one is far from trivial, considering the complexities of tax and employment law in 50 different states.