It's not accurate to say that the NSA (National Security Agency) or any reputable cryptographic body designs secure algorithms with intentional, classified vulnerabilities. In fact, the goal of cryptographic design, especially for public and widely used standards, is to create algorithms that are as secure as possible, free from known vulnerabilities that could be exploited.

However, there are several reasons why the perception that the NSA might design algorithms with "backdoors" or vulnerabilities exists:

1. **Dual Role**: The NSA has a dual role in both creating cryptographic standards to protect national security information and in intelligence gathering, which includes breaking cryptographic codes used by foreign entities. This dual role can lead to perceptions of conflict of interest.

2. **Historical Incidents**: There have been historical instances where the NSA has influenced cryptographic standards in ways that later were found to potentially weaken the security of those standards. For example, concerns were raised about the NSA's involvement in the development of the Dual_EC_DRBG random number generator, which was suspected to have a backdoor.

3. **Classified Operations**: Much of the NSA's work is classified, which means that the full extent of their involvement in cryptographic standards and the details of their capabilities are not publicly known. This secrecy can lead to speculation and mistrust.

4. **Security vs. Surveillance Balance**: The NSA, like many national security agencies worldwide, must balance the need for strong cryptographic standards to protect sensitive information with the desire to have the capability to intercept and decipher communications of adversaries. This balance is often at the heart of debates over encryption policy and law enforcement access to encrypted data.

It's important to distinguish between the development of cryptographic standards, which aim for the highest security possible and are often subject to intense scrutiny and peer review in the public domain, and the specific operational tactics an intelligence agency might employ, which are not representative of the public cryptographic community's goals.