Right, it is not a problem with HTTP. It is usually a problem with buffer sizes of (proxy) server implementations, resources (memory) or practical security conc

Right, it is not a problem with HTTP. It is usually a problem with buffer sizes of (proxy) server implementations, resources (memory) or practical security concerns (DoS prevention). For example, if a proxy server uses a single buffer for evaluating the headers, you end up with a size that is too large for the majority of request, which raises resource and security concerns.