As opposed to hole in a block of wood? Given these were metal and hard to craft, that would be like leaving a thousand-dollar pencil holder on one's desk all day.
>Dr Birley said many examples of stone and marble toilet benches existed from across the Roman Empire, but this is believed to be the only surviving wooden seat.
So the article you link says, in colloquial English terms, that stone and marble toilets from the period are pretty common but wooden toilet seats are basically all disintegrated. Only one (1) wooden seat is known to remain.
And there are people on this planet with solid gold pens in their pocket. People today love flaunting their wealth, and so did people 2000 years ago.