I think the main reason is simply historic. OOP is a lot easier to implement (in terms of reasonable runtime efficiency) than FP. Because of this, it had a huge head start to get itself into common usage. FP has only recently gotten to the point where it is actually competative on performace.
In terms of 'getting it', computers and programing were originally the domain of people who were much more procient in math than now. I suspect many of them would have been more comftorable with FP, but implenting it was way beyond their time.
Object-oriented programming became popular when the number of programmers increased dramatically in the 80s/90s. Most of the high-end programmers do prefer FP, especially as they have the math background to appreciate it. But everyone else...objects have a usability advantage.
I'd really like to hear an argument for this that doesn't beg the question.
Many of the strong programming languages people I have met have been amazing programmers strongly in the "FP" category. If you look at a lot of the PL people that do dev work in Google, they belong to this category as well.
I'm not in that world personally. I attended WGFP once and found people like Simon Peyton Jones to be crazy smart and able to work with through complex abstractions quickly to find very elegant solutions. But I just couldn't think like that, I'm more OO.
Wikipedia seems to say that OOP was invented in the AI labs at MIT. In the same LISP mentioned above. Interesting.
http://en.wikipedia.org/wiki/Cyclomatic_complexity
Much of this work, however, predates the heavy use of indirection and relatively opaque abstractions. In my opinion, functional programming suck on the "understand every bit of the program" metric given the amount of indirection in code (e.g. via higher-order functions, OO languages can suffer also via virtual dispatch and Hollywood principle architectures). However, they potentially excel at "understand the program in the context of these understood abstractions" metric.
Unfortunately, humans are very diverse in their abilities to learn and understand abstractions, especially ones that are based on math. So some people get FP very well, while many others seem to do better with the more naturalistic (i.e. based on natural language) abstractions such as objects. There are good reasons why OOP is more popular than FP beyond the vacuous "they simply don't get it" arguments.