There are many reasons why the proxy IP availability cannot reach 100%, involving technology, network environment, service quality and other aspects. Here are some of the main reasons:

1. Network instability

Network fluctuations: The network connection between the proxy server and the user may be affected by network fluctuations, delays or packet loss, which will cause the proxy IP to not work properly.

Network congestion: Network congestion during peak hours may cause the proxy IP to respond slowly or even be unusable.

2. The quality of the proxy server

Server load: The proxy server carries too much load, which may lead to insufficient server resources, thus affecting the availability of the proxy IP.

Server failure: Hardware failure, software errors or maintenance updates may cause the proxy server to be temporarily unable to provide services.

3. IP blocking and blacklisting

IP blocking: Some websites and services will detect and block proxy IPs, especially those used for crawling, data grabbing or bypassing geographical restrictions.

IP blacklisting: The proxy IP may be added to the blacklist, resulting in inaccessibility to certain websites or services.

4. Geographical restrictions

Geographical blocking: Some proxy IPs may be restricted by geographical location and cannot access websites or services in specific regions.

Uneven IP distribution: The uneven geographical distribution of proxy IPs may lead to insufficient number of proxy IPs in some regions, affecting availability.

5. Proxy type and configuration issues

Incompatible protocols: Different types of proxies (HTTP, HTTPS, SOCKS, etc.) may be incompatible or not work properly in some applications and services.

Misconfiguration: Configuration errors by users or service providers may cause proxy IPs to not work properly.

6. Security and privacy considerations

Detection mechanism: Some high-security websites or services use advanced detection mechanisms to identify and block proxy IPs.

Privacy protection: There are usually fewer proxy IPs with high anonymity or high security, and using these IPs may encounter more restrictions and checks, affecting availability.

7. Market demand and supply

High demand: The high demand for high-quality proxy IPs may lead to insufficient available IP resources, especially during peak periods.

Limited supply: The IP resources of proxy service providers are limited and it is impossible to meet the needs of all users.

8. Legal and policy restrictions

Legal regulation: Some countries or regions have strict legal regulation on proxy services, which may result in the restriction or prohibition of proxy IP services.

Policy changes: Changes in Internet policies and rules may affect the use and availability of proxy IPs.

9. Complexity of usage scenarios

Dynamic content: Dynamic website content or complex interactive applications may place higher requirements on the stability and availability of proxy IPs.

High-frequency requests: Frequent requests may cause IPs to be blocked or restricted, affecting availability.

In summary, the availability rate of proxy IPs is affected by many factors and cannot reach 100%. When selecting and using proxy IPs, users should choose reliable proxy service providers based on specific needs and usage scenarios, and be prepared to deal with unstable factors.