There are a lot more people with allergies these days. Just look at the amount of children who are allergic to peanuts. When it comes to gluten, there are some people with an allergy, some who just have sensitivities, and others who maybe just tried eliminating gluten and realized they felt better without it. Whatever your situation is, there really are a lot more options now than there used to be and substitutes for gluten are more easily found than ever before.
Unfortunately, depending on where you're located, you'll sometimes hear a lot of people that think people who don't want to eat gluten are just making up the ill effects they have from it. Personally, I've not experienced any bad side effects from eating gluten, but if you think you might be sensitive, you can either be tested for it or simply try to cut it out of your diet for a month. If you experience health issues when you add it back in, it's probably time to consult your doctor or nutritionist for a professional assessment.