So, my question is this - Where are these websites these people have designed or developed? Are they on the web? If yes, where, if no why claim that they have done so?
At the risk of sounding sarcastic or like a smart aleck, those websites are out there in cyberspace and all you have to do if you really want, is google for them. You use the right words and you will find them. Nothing is hidden in cyberspace. Yes, worse case it will be on page 50 of the search results but it is there for any to find.
Granted, some websites (like financial institutions and security agencies) would not want the information about the developer displayed on their websites for various reasons. I have developed websites where I charged for them not to have my "powered by justwebservices" displayed at the footer area.
And I am sure some others have done same.
I for one choose (my prerogative) not to share my info publicly. That however doesn't mean that if you were to know the right keywords to enter into google for example, you couldn't find out anything about me. I however invite people (and some people have done so) who are curious to contact me directly if they so wish. I also give such people the condition that they not share it publicly. Whereby they do and I find out, I will stop such a practice. I am personally not the type to blow my trumpet. I am not into the "do you know who i am?" or "do you know what kind of sites I have developed" mind set. It's just me. I am sure I have lost and/or stand to lose from my attitude but if so, hey, I guess that is my lot in life.