Jason Not at all. Optimised hosting is sold on the basis that the vanilla instance of WordPress that the hosting company provides has been tested against various industry benchmarks, and is tailored to the hardware that it is running against.
Unfortunately, where most of this ideology falls apart is when the physical host has thousands of virtual websites running on it, and becomes oversubscribed. Typically, situations like this are masked by the use of technologies such as Litespeed and other caching mechanisms. Great if you have a static site that never changes, but can be viewed as a negative if you have a site that is dynamic in nature, and includes user login sessions.
These should never be cached - and if they are, the cache should at the very least be "private" in the sense that only that user session has access to it.