why do all vegetarians expect all restaurants to change their menu's to cater to their wants?

I have not seen too many pushy ones but haven't looked for that either. I think it is nice though that more restaurants are emphasizing vegetables. There is so much unhealthy food, that when I run across one that is specializing in delicious and yet nutritious foods, it makes my heart happy. :) Sounds like you had a bad experience.

I don't expect this of all restaurants, and I'm a vegan. I think it's a good idea, but I'm not going to petition to KFC to get more veg options on their menu. I rarely go out anyways, it's costly.

I would say that most of them are making suggestions to the restaurants menu, not "tell[ing] other people how to run THEIR business" and if restaurants want to increase their sales, they'll be amenable to suggestions and menu changes.

Now, if they're demanding that the restaurants change their menus, then they either need to take a more relaxed tone, or speak with their wallet, and not pay money for those restaurants.

If I were running a restaurant, I would put out a suggestion box, a place where people can write reviews and suggestions. If enough people wanted a new idea instituted, I would follow through with it. We in America live in a capitalistic economy, and our businesses stay alive because people fuel them with their money, and people will only spend there money in these places if they cater to their desires.

What do you mean by that? Why do they offer vegetarian options? Simple answer is money. They are paying customers. Any restaurant worth its weight should be able to offer exciting meals for any of their guests.

Because most are able and willing to, and it's business.

Because they are all self centered!