The point I'm getting at isn't to promote the nuclear option, but suggest that maybe there's a good reason for e.g. a web browser or your word processor to not have the same privileges as a user who can execute "simple administrative tasks" like changing the TCP/IP stack through which all your network traffic passes.
Most personal computers do not need server processes (unless you want to connect remotely to them), but your question was not restricted to them.
That being said, check out capabilities(7) in Linux. You can grant an executable the privilege of binding to a low port when run by non-0 uid through setcap. This is a good compromise.
ssh and smtp generally need root to do their job, although maybe you could find a way to deliver mail to users without it. If you want to run user based dns or others, you could set the priviledged port even lower.
