I am putting my thoughts on this, please share your thoughts, comments.
Request length is less than the response length.So, processing small amount
of data is better than of processing bulk data. Response may have encrypted
data. Buffering all the client-server transactions and validating signatures
on them is difficult. Even though buffered, client data may not be in the
plain text. Embedding all the client encryption/decryption process on the
fly is not possible, even though ips gathered key values of clients.Most of
the client protection is done by anti-virus. So, concentrating client
attacks at IPS level is not so needed.