Maybe nobody works for the end user ever, but some people work more for the end user than others.
If you work for a web site that makes its money by lead gen or advertising, you're often working against the end user. This isn't necessarily true, it's just how the incentives will align.
If you sell SaaS to the enterprise, you're not working for the end-user, you're working for their boss, or whoever else is making the purchase decision.
If you're selling a product directly to end users, and usability is a factor in whether or not they choose pay you, that's a little closer to working for the end user.
And, best-case scenario, if you are the end-user, or your boss is the end-user, then you can truly be working for the end-user.
If you work for a web site that makes its money by lead gen or advertising, you're often working against the end user. This isn't necessarily true, it's just how the incentives will align.
If you sell SaaS to the enterprise, you're not working for the end-user, you're working for their boss, or whoever else is making the purchase decision.
If you're selling a product directly to end users, and usability is a factor in whether or not they choose pay you, that's a little closer to working for the end user.
And, best-case scenario, if you are the end-user, or your boss is the end-user, then you can truly be working for the end-user.