It does seem to have become very common for B & B's in the UK to ask guests to remove their shoes at the door. It is encouraging that they feel able to ask this of paying customers. It makes sense to do this as they are taking in visitors into their homes on a regular basis. They don't want their carpets or flooring ruined.
It seems to be most common for bed and breakfast places in the Scottish highlands to ask for shoes off. That is unsurprising, as their guests are going to be doing a lot of walking. However, there seem to be a fair view bed and breakfasts on the south coast and other parts of England with a no-shoes policy.
It sometimes gets negative reviews on TripAdvisor and other review sites. I suppose it is part of the different experience of the British 'Staycation.' People may be used to holidaying abroad and staying in hotels where they can keep their shoes on. Staying in somebody's house and having to shed the shoes may seem a bit strange for a lot of holidaymakers.