@OP: Hi. I'm the nicest and most thoughtful person around these parts and take great care to make everyone feel welcome so I am obviously going to be very kind with my response to you.
Good Sir, thank you very much for your warm and loving welcome.
1) The concept of tipping is kind of foreign in my country, so I did not know that. I appreciate the information.
2) You compare the system to giving money to a beggar on the street holding out his hands. I would rather compare it to a street artist, who actually offers something (music, paintings, performance) which may or may not be of worth to bypassers. Personally, I like to give a coin to street performers when I enjoy their work. In this way, I can also ensure that the artist may come back some other time to delight me again with their skills.
I have seen people in online forums who invest a ridiculous amount of time and energy to write detailed tutorials, or to help out helpless newbies. Often I have wished to give them s.th. back for their efforts. These people have offered their advice many a times, and will probably continue to do so in the future. So I disagree with your opinion that I would not get "value for my money", as the job has basically already been performed, and with my donation I may even increase the chance of more jobs being performed in the future (in the form of more tutorials and advice and stuff).