I dont have any statistical evidence but there are probably some “fee based” advisors who either do not discuss, or recommend, Roth conversions because they will manage fewer assets.
Since Roth conversions are very client specific, it’s difficult to prove whether someone is recommending against it because it’s the right strategy or if they have an ulterior motive. To be clear, Roth conversions are not in the best interest of everyone but it may be appropriate for some.
The irony is if these advisors were pure commission based and got paid upfront (without an annual advisory fee or received trail commissions), they may not have the same conflict of interest for future assets.