Answer
1. Agile can not be used on every project.
Agile methodology involves the use of an adaptive life cycle on a project instead of a predictive life cycle.
When it’s not possible to predict the product, an adaptive life cycle can be used; hence the need for agile methodology arises.
But, that's not always true because projects need to be delivered incrementally and developed iteratively.
Project being delivered incrementally means that some projects requires that its usable” subsets be done, step by step, instead of delivering once at the end of the project in agile.
2. Notable reasons for not always using Agile
1. Reliance on legacy methods
2. Lack of clarity
3. Inadequate Experience with agile
4. Lack of alignment in other areas of the enterprise
5. Lack of a Testing Strategy
6. Lack of collaboration in teams composed by different companies
3. Why agile would not be the most effective and efficient methodologies
1. It is too flexible
2. Lack of predictability
3. Difficult to Integrate Diverse Skill Sets Into Teams