Response may be due to question format. May have needed to be a bit clearer. Those answering yes agree that if someone goes out to buy something to sell for profit they should be considered a business (which is a clear business requirement seemingly
in the UK. The other respondents "just don't care".
Issue with your question is that UK business laws vary from USA business laws. In USA laws vary from state to state, and USA citizens are under the jurisdiction of their own state business requirements and federal requirements. So it's kind of like looking at apples, oranges, bananas, etc.
It would be important for each person to be aware of requirements that affect their business practices, and choose their activites accordingly.