1) Because let's be honest, it isn't necessary. It's sad but true. And if something isn't necessary motivation goes down a lot for most people. If you are an American who lives their whole life in the USA you only need English. The USA is so damn enormous that you can travel for hundreds of miles in any direction and only ever have to be able to speak English. The neighbouring countries pretty much speak only one other language in Spanish (in Mexico and throughout South and Central America, with the exception of Brazil).  Try that in mainland Europe and see how far you can get only speaking your native language. 

2) English is taught everywhere as a second language. What you describe is not a uniquely American phenomenon, it happens everywhere where English is the first language. The situation is equally bad in the UK. Hell, I am a native English speaker currently working in English in a country in mainland Europe, where 95% of my colleagues are non-native speakers of the language. It's simply a fact in a globalised world.

3) Languages are taught badly everywhere. They are treated like any other subject, something to pass or get a good grade in. There is not enough emphasis on communicating yourself which is the fun part. Without a way of generating intrinsic motivation in a person, they will get demotivated and quit the moment it gets a bit difficult. 

Many people are lazy. This isn’t a national thing. This is especially true when the reasons for doing something are extrinsic and not intrinsic. They usually don’t have the inner drive to do what they need to do and are either too lazy to do it or try to find the easiest route to get where they need to be.

I used to be an English teacher in my own country (taught in a language school and gave private lessons), and people’s lack of motivation was so incredibly demotivating that I couldn’t take it anymore. I had students straight up ask me if and how they could cheat on the IELTS. I had students who were happy that they barely passed the course we were doing. I had students who slept through classes. I had students who seemed very serious at first but it took one or two lessons for me to find out they didn’t actually have the drive to commit to learning a language.

I’ve come to realize that many people want to learn a language, but few actually go through with it. This is why.I appreciate committed and dedicated students. They make the work worth doing.

Guyomar:

Skilled expats (usually Westerners) in the Gulf Arab countries often like to follow their own culture and break the customs and laws of the land, and when they get caught, they do sometimes play the victim. A few years ago, a British couple was caught having sex in public in Dubai, and people seriously tried arguing that their human rights were being violated. Apparently having sex in public is a human right.

Some people quite overtly claimed that our countries were backwards and as such our laws shouldn’t be respected.

As a matter of fact, it’s incredibly common in the Gulf for everyone (including authorities) to turn a blind eye to well-off expats. Even in Saudi Arabia, where alcohol is prohibited, some expats have their own compounds and sometimes have breweries in them for themselves. This is an open secret. And in some countries, such as Qatar, there are explicit laws differentiating locals from non-locals. If you’re a local, you’re not allowed to drink alcohol. If you’re not a local, you can get a license that allows you to purchase alcohol. This is done specifically to cater to Westerners, because they bring in the money.

When it comes to language-learning, it’s often the unskilled and semi-skilled foreign workers (usually South Asians and Southeast Asians) who need to learn the language, to communicate with the locals. Westerners, who are usually skilled workers, don’t learn the language, and in fact locals often need to learn English to communicate with them. I have had so many local students tell me they need to learn English for their work, because their meetings are in English—in our own country. The only Westerners I’ve had as Arabic students wanted to learn Arabic out of their own interest. There is simply no expectation for Westerners in the Gulf to learn the language or integrate.