Once of the most common issues I hear when it comes to Agile adoption is the "lack of estimates." I'm not sure where this notion comes from precisely. Looking at the manifesto and principles, there doesn't seem to be mention about estimation directly, but I suppose it could be construed from this one line of the manifesto:
Customer Collaboration over Contract Negotiation
The terms contract and negotiation have fairly negative connotations in my mind, but perhaps the business folks are more comfortable with them. After all, the work of software is to perform a service or operation in some way which saves or makes an organization money. Any time the business spends money, this is why. The customer doesn't care about PHP or HTML5 or NoSQL; your system could run on Unicorn blood and Kraken oil so long as it solves their problem. You deliver a product or service which solves a problem and they are paying you to help them solve it. Contracts are the formalization of what it means to solve their problem with the understanding of what it will cost to solve that problem. Negotiation is the process of establishing a contract, so that all parties have a common understanding.