I wonder if people have been brainwashed by all the ads for bacteria-proofing everything in sight? Basic standards of housekeeping would ensure that floors don't have 'dog wee, spit etc' on them for very long. If, in the time between the unlikely event that people have trodden it in and the next time the floor is cleaned, anyone has licked the carpet then they might be at a minute risk of something or other, but only then if they have an immune system weakened by illness or underdeveloped because of under-exposure to bacteria or virus.
It is not realistic to see it as a hygiene issue, surely? It is a preference that some people have, as is obvious from this thread, but I can't help thinking that the talk of dog wee and so on is just to justify that preference. Dogs wee on trees or lampposts, where shoes rarely tread.
I do think that the current trend for 'anti-baccing' clothes, toys, surfaces and everything else is (a) to increase the profits of manufacturers, and (b) weakening the immune systems of those who do it. I know that's a slightly separate issue, but I wonder if there is a link.