I want to order samples from those companys that really send you samples. ........ I'm a hobbist of robotics.

You may just have indicated why some companies are reluctant to send samples.

I do realize that it often is difficult/impossible to buy something one off and requesting a sample is more likely to succeed, so this is not a comment on your request, but on the state of the distribution chain.

The only company where I have been successful in getting samples from when no personal relation or volume purchasing company was involved has been Maxim. Then, of course, Maxim is next to impossible to buy less that thousands from.

One word of advice:
Invent a company name, you are more likly to get samples sent to Acme Widgets, att. Joe Blow than just to Joe Blow.

Erik