To make someone feel happy, appreciated and welcome.

G'day Tempter, Thanks for your question. It is a personal decision as to whether or not someone responds. However, it helps to build a stronger community and acknowledge people's contribution. I have started to welcome new users in order them to encourage them to stay and contribute. Unlike Yahoo! Answers, we don't have one of the most popular search engines on the web promoting us. We need to ensure that we have a friendly atmosphere for newcomers. I consider that it is the equivalent of inviting newcomers to town for drinks. It makes them feel that they are amongst friends rather than strangers. Regards

to maintain a sense of community here.

Could be to distribute fluff points, much like this question.

Tempter I personally only ask congratulations questions when I either personally know the user or a friend of mine knows the user and asks me to do them a favor and post a congratulations question. As far as I am concerned I could care less if anyone gave me points for the question. I don' t ask those sorts of questions for the points but rather to recognize the accomplishments or a special occasion such as a birthday of the person being congratulated because I care enough about them to make sure they get the recognition they deserve. As far as the welcoming new users questions go unless I personally know the person I will never ask that kind of question because I agree someone asking that type of question who doesn' t personally know the user is either doing it just to pander for points or wants to get on the new users good side so they think by asking a question about welcoming the new user said new user is gonna fawn all over em. Personally if I believe that the asker doesn't know the person being congratulated or welcomed I assume it is just a ploy for points. It won't stop me from answering that kind of question but usually I won't give the person points for asking.

Again that's the beauty of this site. You can pick and choose what you answer. You don't have to congratulate anyone or welcome anyone. I do it because that is how I am....I like to make folks feel welcome.

Common courtesy

Because we are just such a friendly lot now aren’t we?

We congratulate people because of their achievement of reaching said level! I only congratulate people of lv50, 60, 70 ect. as these are the levels that, imo, need alot of effort and community spirit to achieve. I only welcome people when they are friends of someone I know and like on here.

Whenever I see a new person I drop into their answer and say welcome. It is a part of what we are on the Bag:)

AB is a constantly changing and growing website. It has grown from just a simple Q&A site into Q&A/debate/fun/social website.

I always say g'day and welcome to any 'newbies' that happen to fall into the AB web and tell them to quit struggling its useless...lol I was welcomed into the AB family by many fellow ABers ..the same ones that still do this and its a tradition I think is one we ALL should continue to do ...as far a congrats go ...great! a little recognition by your peers is always welcome and it strengthens the community spirt here on AB and thats always a good thing

to be polite there`s enough crap in the world today

Your use of the word "should" in your question makes it sound like you feel compelled, or would like to compel others to do it. I hardly ever even look at the names of who asks or answers questions, unless they catch my attention, therefore I don't know when new people/levels come up. I sometimes notice if the same person answers the same questions I do a lot, or gives questions I particularly agree/disagree with. I almost never notice levels.