Why do friends forward emails?

Today I got a forwarded email from a friend of mine. Talking about forwards, I hate those good luck and bad luck ones. I am not bothered about all these things, nor do I believe in bad luck affecting my very existence; but how do I react people send me chain messages saying that "if you don't forward it to 5 or 10 people within the next 2 minutes, you will have bad luck for the rest of your life", or that "Microsoft/ Bill gates has just announced the most dangerous virus released till now" or recently "Orkut/ Yahoo is going to delete the address if you do not forward this mail"; not to mention using God's pictures and other rare photos to pass on this information?

I don't want to offend people, but I get to irritated seeing such junk mails filling my inbox, that once I wrote a very rude mail to my friends through 'Orkut messages'; got many responses to that too. But there are some of my "dear" friends who do not seem to get a clue even after seeing such mails from me, I can plead, beg, order, shout, what else? When nothing works, endure it. Just keep deleting such mails, hoax messages and chain messages, everything deserves to be in the trash box of my email, or even permanent deletion.

Whenever I get a forward (depending on my free-time available) I do a google search to see if there's any website which has information about this. If its a hoax, I get some link to 'urban legends'; am not sure of the website, but it just takes a minute in google. The funniest part is that these forwards would have changed in name and form, new virus names, often more powerful curses for not forwarding... So I suggest that my dear friends please take a minute (it takes less time than to enter all your friends' email addresses) before forwarding to people and think about the time you are wasting, yours and others. Obviously if its something really important, would it not come in cnn or bbc or atleast local paper headlines. I don't know whether its just me, or do others also get irritated sometimes seeing their inboxes with junk forwards, the first thing in the morning? And, would even friendship get affected because of these annoying mails? Something to think about...