Why projects fail

A project is considered a failure when it has not delivered what was required, in line with expectations. Therefore, in order to succeed, a project must deliver to cost, to quality, and on time; and it must deliver the benefits presented in the business case.
So here are the main reasons for project failure:
The wrong business requirements have been addressed- If your project is set up to deliver the "wrong thing," it may be considered a failure even if everything is delivered on time, within budget, and to the required quality. Because for example if you set out for the project to appeal to teenagers when actually the target audience was people 40+ then the project would have failed its intended purpose.
Governance is poor- few projects ever start without a sponsor. This is the person who has identified the need for change in an area of the business, and who is committed to making that change happen. He or she plays a vital role in ensuring the project's success. A good sponsor can make a mediocre project fantastic, and a poor sponsor can delay and frustrate a fantastic project team. The project sponsor is supported by the project's governance bodies, usually in the form of a steering group (this is a group which provides professional ownership and strategic direction, monitors the performance of the project). These governance roles are essential: they provide direction, guidance, and critical review of the project and its progress. As project manager, you're involved in the day-to-day running of the project, but governance groups can take a step back and look at the project from a different perspective. They can ask difficult questions about progress and performance. They may see things that you've overlooked. However, they can also support you by providing contacts and insights that help you get things done, and by providing "political cover" when you need it. Project managers don't usually have any influence over who their project sponsor is. Sponsors either self-select, or they're chosen because of their position in the organization. However, you often have more influence over who is in your steering group.
Implementation- if you start off with a bad implementation plan your whole project will not work as the implementation plan is what gets the project going and working so for example if you allocate some resources to the wrong place you be in a mix up and then your project will have to stop therefore you will have delays which will the then affect everything else.
People lose focus on the project's benefits- Projects are based on a list of benefits that must be delivered. For example, you may need a faster customer service process, you may need to produce products more cheaply, or you may need to improve the quality of your service. These benefit statements should be refined so that they're clear, concise, and quantified. From these benefit statements; a set of "things to do" is generated. For example, you may need to consult customers, redesign products, or implement a new system. The outcome of this is a business case document that analyses the project in terms of costs and of the benefits will be delivered.
Environmental changes- If the business needs change, then your business case can become outdated before you've actually completed the project. You may have to review your original requirements and goals partway through the project to decide how to proceed, and this may result in changing the scope of your project so if you cannot change your plan because you can cannot make timely decisions and you haven’t seen that the project will not be able to deliver what is required you should have implemented change which will then make the project suited to the environment you are then in.
NHS IT Project failure (2011)
The NHS project (launched in 2002) was to create a system called the E-records system which would keep all the patients data on so all staff could access it with ease but