If you can still carry COVID-19 and transmit it while vaccinated, why do some places have travel restrictions for the unvaccinated but not the vaccinated (e.g. Switzerland)?

Switzerland travel restrictions

Because they require testing immediately before travel in addition to vaccination.

It is the combination of vaccination and testing that makes travelers safe enough to be allowed in.

Vaccinated or not, you canu2019t transmit it if you donu2019t have it.