Well, unless we reach the limit of physics, "we can't" is always synonymous with "we don't want to". And it's usually a matter of resources, values or skills.

Well, unless we reach the limit of physics, "we can't" is always synonymous with "we don't want to". And it's usually a matter of resources, values or skills. But it's bad PR to say "we don't want to spend that much" or "we are not skilled enough to do it". So big entities always say it's against moral/law to do it, or that it can't be done.