I'm sure you won't be surprised a bit about my comments 😀
it is intended to correct only the problems that are described in this article. Apply it only to systems that are experiencing these specific problems.
if you are not severely affected by any of these problems, we recommend that you wait for the next SQL Server 2005 service pack that contains the hotfixes in this cumulative update package.
These are two quotes from this KB article on CU8 for SQL2005 SP2. All other CUs I checked have, and always had, the same or similar advice. Many companies will take this advice seriously, so until they run into real problems, they will avoid the CUs and wait for the next SP.
Another problem I have with the "no SPs" policy is that this text above is, maybe not explicit, but at least implictly a promise that there will be a next service pack. How can you tell customers to wait for a next service pack, than not release one?
So yes, I do think that service packs should be released, and on a regular and predictable cycle. The first one 6 months after RTM, and then a 12-month cycle. Unless really serious or annying bugs are fixed, that should warrant an intermediate extra SP (or, better, a CU with a different advice).
Either that, or increase the testing of CUs, advice customers to install each CU, and abandon SPs completely.