If you are happy with contact lenses and don't find them uncomfortable and it doesn't interfere with your chosen lifestyle, then why have an operation? If, however, for example, you can't tolerate contact lenses, like to swim and do water sports, find glasses do not provide you with the all-round vision you need to enjoy your chosen activities even when they aren't splattered with water, and are short sighted enough that you would be severely disabled if your glasses were knocked off your face, then it is worth considering and probably worth several thousand pounds to get done. Likewise, if your chosen profession requires you to have vision that does not fall below a certain standard. Basically, you would want the immediate potential benefits to be so great to you, personally, that you would be willing to take the risk of dry eyes and other possible side effects, as well as long term future uncertainty. The risks of the operation these days going badly wrong immediately are exceptionally small if you go somewhere with an excellent reputation - the likelihood is that you will get fantastic vision with no noticeable issues over the next 10 years. Not having your eyes done, of course, brings the certainty that you will never be able to see very well and your eyesight will only get worse as you get older.
One point to bear in mind if you are very short-sighted, is that as you get older, it gets phenomenally expensive to get ultra-thin multi-focal or bi-focal plastic lenses for glasses, so you might have to start wearing very heavy, thick lenses again when you wear glasses. Not so much of a problem if your eyes can and continue to be able to tolerate contact lenses, of course, but I certainly found with my prescription that the weight of anything but very thin and light lenses in my glasses gave me a dreadful headache and irritated my nose and ears, not to mention looked pretty unsightly. Still, who knows what will happen to the eyes of people who had laser eye surgery to avoid this eventuality, as they age? It's not that long since laser eye surgery started. But then, soft contact lenses aren't so very old, either, yet people happily stick those in their eyes as though they know all the risks.