Many blogs and articles have been written that cover this subject and I just wanted to add my own two cents. Why is it so hard to introduce agility in the workplace. There are many reasons, but I have to say that top of the list is that its just plain hard to change people. Most folk have a comfort zone beyond which they simply don't feel happy going. Agility is so much more than just another process, its much more of a culture change than anything else, and its very hard to bring about culture change.
Whatever you're trying to change, you're always going to face resistance, because change could affect someone's role in a way that alters their stake and they (sometimes justifiably) fear the unknown will land them in a less desirable situation than the one they're currently in. Before doing anything in your organization though, analyze the situation, don't introduce something just for the sake of it, there has to be a good reason.
The implications of introducing agility will be far reaching and very uncomfortable for many at least initially. Also consider whether or not you actually have the raw materials to enable agility to happen. For example - are you going to have ready access to your customer? If not, this is a huge problem for any agile method - which works on the premise that frequent face-to-face communication is one of the best ways of loading the dice in your favor. With this example a good idea (I believe) would be to dip your toe in the water and see if you can run a small project with all the customer support you need to see if the idea will be welcomed. If not, don't even bother trying to introduce agility yet, your company is simply not ready to make the commitment. Most organizations, are in this stage and most of those who claim that they are agile are not, whether they think so or not.
I used to believe that it was an all or nothing proposition - and as far as declaring 'am I agile' is concerned, then it definitely still is. However, when it comes to introducing it into organizations, its far too much for most people to stomach at one sitting. So is it possible to introduce elements of agility? I think so, as long as you don't blame the principles and practices if they don't work for you, because most are designed to work cohesively together to produce results. Of course there are elements of danger breaking these up, because if you don't understand how things work together you could be staring trouble in the face. For example, refactoring and test driven development go hand in hand, try refactoring without tests and its like walking a tight rope without a net. Ideally, principles and practices should be used as they are so that you can learn how to crawl and then walk before you run, but its tough to introduce things in a big bang fashion.