For the first type of role, you're essentially hired help to solve non-technical problems in broken well-capitalised businesses, whereas in the second you're hired individually for your own skills. The second type are normally much more flexible with respect to remote and lack of travelling.
Take health insurance: I'd imagine employers are buying plans offering per-employee costs lower than if each employee were paying for their own insurance. Economies of scale, bargaining power (at least when it comes to larger firms), etc.
Perhaps at some firms the processing costs really do outweigh the savings, but I would expect this to be the exception rather than the rule.
I could be wrong -- maybe someone with experience could shed some light here.
There were companies that offered full, proper health insurance, but I had my own so the value was close to nil, and the salaries were 25% lower than the smaller companies offered.
Benefits tend to be mostly flat across employees to make use of economics of scale. I'd love something like a company car, and would happily take a salary cut because they're liabilities and it's a win-win where taxes are involved. But if a company won't offer a car to everyone, it's not going to happen. I got free parking as a benefit once but only used it a quarter of the month because it was cheaper to Uber to work. I know they were paying for the parking every month and I'd rather take the cash, but I wouldn't turn down an extra $30 of savings even though it cost them about $100.
In my opinion, we should do whatever maximizes product-market fit.