system
Given the following post, respond as if you're commenting on Reddit:
human
EILI5: Why would the UK leave the EU and what would be the consequences? 

I'm really behind in the subject after being in the US and my French friends seem somewhat biased.... Please, like I'm 5.
gpt
ELI5: The UK feels the direction the EU is going in is harmful to their economy. The focus on higher taxes and regulation especially with regard to Banks and a proposed Financial Transaction Tax would do a lot of damage to the City of London which is the second most important financial center in the world(1st is Wall st). The City of London is very important to the economy of the UK. The UK also feels that certain countries(France,Germany) are not acting in the best interests of Europe as a whole, and would seem to be centralizing power, and to a an extent removing anyone who opposes the decisions that they have made(George Papandreou of Greece)

So essentially the reason they would leave the EU is down to the fact that the EU no longer represents what they signed up to. They are unwilling to cede any power to Brussels which is an important part of increased integration. 

What would happen? Nothing drastic, The UK would just join the European Free Trade Agreement like Norway and Switzerland, and this situation would protect the City of London and by extension the wider economy of The UK.

An important thing to remember is that The UK has a large group of Euro-skeptics, that are becoming increasing vocal as The EU tries to impose stricter rules, which they see as a loss of sovereignty and free will. The UK has never been as pro-Europe as countries like Ireland and Germany so bending to the will of the wider European community is not in their interests.