Behavioral finance lesson – frequent flyer points?

Here is an email that I got last week from a financial planner:

Dear Dan.

My hourly model lets clients use whatever retail custodian they like.  For various reasons, I tend to recommend the two best as Vanguard and Fidelity.  I go over the pros and the cons for each and, as soon as I mention Fidelity gives 25,000 frequent flyer miles, most clients stop me and choose Fidelity.  Some will move tens of millions to Fidelity in order to get frequent flyer miles that might have a $200 economic value ...