Road bikes aren't my thing, but wider tyres make sense for a tour for a bit of extra comfort and versatility.
Depends a bit where you are touring.
Here in the north east we have long sections of gravel/cinder track on which 25/28 or even 30+ tyres are best.
Elsewhere in the country, you might be 95 per cent on minor roads for which skinny roadie slicks are fine.
Another pointer is that which is fitted to touring bicycles - most have 28 tyres or wider.