Can a cultural practise be defective? In the case of British etiquette, I think so. In many cultures across the world, people do not wear shoes in homes. In virtually all of Asia, in the Middle East, in North Africa, in Scandinavia countries, in Canada, the North-western USA, and in Eastern Europe, it is usual to remove one's shoes at the door. But not in Britain. Not in Britain, where we have damp, wet and miserable weather for most of the year.
In Britain, most people will often wear shoes in their homes, ruining their carpets or marking their wooden flooring. It is certainly considered very impolite to ask your guests to remove their shoes. A lot of people will avoid wearing shoes indoors, but they rarely have a consistent policy of removing them at the door. It is common for people to offer to remove their shoes when visiting a friends home, but this is deceptive. The host, according to unspoken convention, must always enthusiastically decline this offer.
I think this is a serious defect in British culture. Wearing shoes in homes is simply stupid. Why have a carpet, or PVC flooring or fine softwood flooring if you intend to walk on it in shoes? Why not simply leave a concrete floor? If you walk on a carpet in shoes, it will wear out a lot faster. If you walk on other kinds of floors in shoes, you will probably leave marks.
There is a health issue involved. Dust is bad for you. One does not generally notice it, but one's shoes pick up dust. Children living in a dusty home have a higher risk of developing asthma. Carpets absorb dust very easily, but even if you dont have a carpet, the dust will build up unless you clean it regularly. Shoes also pick up other stuff, like pesticides, dog excrement (even just traces), petrol fumes and other toxic stuff. Is it really a good idea bringing all this stuff into one's house, or other people's houses?
Perhaps your guests might be embarassed to remove their shoes. Well, provide them with slippers. If people in Eastern Europe can afford to provide their gusts with slippers, I am sure people in Britain can.
Perhaps those bagless Dyson cleaners will help change the British people's attitudes. Those things enable you to see the filth that gets into your carpet. Perhaps also the increase in travel to Asia and the increase in immigration from Eastern Europe will have an influence in persuading British people to shed their shoes at the door.