I think the reason this is not taking off is because the "value" of the vaccine for the traveller is precisely zero. The value of the vaccine is only for the country - and only then if enough have been vaccinated to provide herd immunity.
Why do I say this? Well, if you think about it, who is the same (sereologically) as a vaccinated person? That is, possibly able to get sick but if they do only very mildly, possibly able to transmit but nobody is sure? Basically that's a kindergarten kid.
And we all know how that's working out.