It's about time people were allowed to make informed decisions based on risk assessments they make; otherwise, frankly we'll be running out of places we're "allowed" to visit.
To that end, personally I would be happy to visit Tunisia or Egypt today - but only to the main resorts.
People are generally allowed to holiday where they choose; the FCO simply offers advice on the matter. But if you do choose to holiday in a destination with a known issue, you may find that insurance companies will refuse to offer you cover - why would they? In fact, they don't pay up for terrorist-related losses anyway. Meanwhile, tour operators must focus their programmes on resorts which they can market to customers at a profit. Flying a one-third filled B738 to Egypt is a huge loss-maker however brave and intrepid those passengers may be. And they have to account for the liability risk as well.
Meanwhile, US-style mass-shootings (whilst deeply regrettable in their own right) do not have a track-record of targeting the tourism industry. In countries such as Egypt and Tunisia where outrages are generally motivated by depraved 'religious' fanaticism, attacking tourism is viewed as a way to undermine the economy and the credibility of the governing regime. Hence tourists are a preferred target of choice for the brainwashed medieval savages.