I love a great smile and while I suppose it isn't mandatory that your teeth be straight and white, it certainly does help bring if you have it all together with your pearly-white smile. People that smile, seem happier, and bring more happiness to others. Although, like a lot of things, smiles can be faked, they can also be quite spontaneous and very natural. When you see someone with a genuine smile it makes you feel good. Smiles are just a more effective way of making others believe that you like or care about them.
Although a good smile isn't a requirement for employment and social settings it is certainly a wonderful benefit for both. People that "light up the room" with their smile are the type of people that captivate you and make you feel good about them and yourself. A smile can ease the tension around a personal or group session and can bring people out of their funk or shell in a very positive and emotive way.
Smiles are excellent in making people feel acceptance and it further helps to relax them. A sunny disposition and a smile seem to go together and that is why we equate smiles with people that are either happy or in a good mood or both. A smile is a wonderful way to greet somebody because it allows the other person to smile back in turn, sort of creating that "I'm OK, you're OK" vibe.
A wonderful smile is a great first impression, it's a way of saying, "I like you, I'm interested, I value you," all rolled into one. Having a great smile is much more important than a great handshake because the smile comes first and at a further distance. Also, for those with great smiles and teeth it is a subtle way of saying that you're healthy, have good hygiene and all the rest that is implied with it.
If you don't have a great smile, is it worth doing so? Of course, it is. I am grateful that I received braces at a young age to correct my protruding teeth. Although as a very young teenager I wasn't particularly sensitive about my teeth, as that was well before my dating years, I was also savvy enough to know that I certainly desired to have them corrected. Had my teeth remained the same as they were with my two noticeably front teeth protruding it would have absolutely affected me in a very negative way. I have no doubt that I would have dated less, been less confident about myself, less popular, less desirable, less successful, and much more introverted. A good smile is worth every penny of the expense and the trivial inconvenience and pain.
While there may be plenty of things you can do or accomplish to make yourself a better person a smile is certainly one of those things who's worth is far beyond superficiality and will bring you and others a lifetime of satisfaction and pleasure.
As Louis Armstrong (he, of the prodigious talent and great smile) sang: "When you're smiling, keep on smiling, the whole world smiles with you."