I'd argue that more or less every restaurant already has at least one vegan 'option', although not necessarily a good one. If they have french fries with ketchup, or bread and margarine, they already comply with a hypothetical law.

And I don't see any way to mandate "offer at least one delicious option" as that's up for debate and nothing objective.

I guess more and more restaurants are adding vegetarian and vegan options nowerdays purely because there's a demand for it. If there's a group of five looking for a restaurant where only one of the group is a vegan, most groups will pick a restaurant that caters everyone's needs. Thus, having no such option will result in less customers and less income.

I see no reason why a restaurant should be forced to cater to everybody.