As my lawyer always likes to say, include it in a contract if for no other reason than to further muddy up the waters enough to make a client not pursue a claim, or to drop it once their own lawyer dives into the signed contract's language. Between my E&O carrier's engagement letter, IRS due diligence and required information forms, and additional agreements I have decided to include, my engagement packet for individuals is 33 pages. I do not feel the least bit bad about it or find it unreasonable--it is high risk and there are a lot of terms associated with it. Just as lack of understanding of the law is not an excuse for violating it, neither is not reading a contract's language unless it was clearly written to be confusing.
When I send the returns to my clients, I tell them they need to review and to let me know if they have any questions. Based on lack of questions, overall, I am certain almost none of them even glance at it, other than to know what they owe or will be refunded. SMH