> it's a very naive thing to think that it's just "customers/suppliers" looking at who they're dealing with

Its still no excuse.

Nobody forces anybody to start a business.

If somebody chooses to start a business then they should do grown-up things like having insurance and complying with the law – which includes publishing their business's contact details.

The legal and good manners reasons for publishing a business's contact details far out-weigh any negative ones.

I am sure I am not the only person on this planet who associates alarm bells with small/medium businesses that try to hide their contact details on their website. As a customer it rings alarm bells that they are going to be a pain the neck to deal with if something goes wrong – if a business is trying to bypass such fundamental requirements, then it makes you think about how they feel about e.g. consumer rights law in relation to handling returns.