Why is spanish the most popular language to learn? I know that it is one of the most widely known languages in the world, but wouldn't people be more interested in learning a language that is not as popular?
Some people really love the language, some do it for work or university, some because they want to communicate with more people, get a taste of the Romance language group, or all of the above. A lot of people here on DL are learning other languages also. There are more Spanish speakers in the USA than in Spain, so that is also a reason. The Western Hemisphere is dominated by Spanish, obviously found in Spain and you can find it in some parts of Africa (Equatorial Guinea for example), the Philippines and I'm sure other nations in the Eastern hemisphere it is recognized.
In some parts of the US, there are communities that speak more Spanish than English, and if you're trying to live or work anywhere in those areas, being able to speak Spanish is necessary. I suspect that a good deal of the people in the US who are learning Spanish here are doing so at least partially to make themselves a better job applicant.
The only reason Spanish is used so much in the USA is because we have a bunch of Mexicans living here that are intent on not learning English. It seems that every other country except the US require you to learn the official language. (I don't have anything against Mexicans by the way)
I think it's about half and half. There are a lot of motivated ones but a lot of ones who are content living in their Hispanic community and working as laborers. I know the way they live is still better than they had in mexico, but they could make it even better learning English and getting a better paying Job. I personally know both kinds of Mexicans.