At this point, few are so scared of the virus itself that they wouldn't step out of their homes and engage with all the normal activities, albeit with safety measures in place. And that includes travel. The number of people who fear getting infected on a plane these days is a lot lower than 6 months ago. Most of those who do have genuine concerns related to their age and physical condition which, absolutely reasonably, make them go the extra mile to protect themselves.
The problem why the "test and travel" concept would still be highly unappetising to everyone whose trip is not essential is uncertainty. If you're asymptomatic or unlucky enough to trigger a false positive result, your trip will be snatched away from you two hours before departure. If it's a family, that's even worse because everyone will go into quarantine instead of a vacation. Hence, many will prefer local holidays not involving this sort of gamble until something smarter comes into place. Like maybe the realisation that imported cases are no longer a big problem (unless you're New Zealand or one of the few other places where the dreaded lurgy isn't widespread). Or a decent vaccine and an immunity certificate instead of any entry restrictions.