I doubt the LBS wants every curious tirekicker to walk in off the streets and take a tri bike out for a spin. I also doubt that they feel that the bike is shown in its best light with plastic pedals slammed on. So they either expect that you are experienced enough with this kind of equipment to bring along your own pedals/shoes or they limit test rides to customers that they have a history with and know that they are familiar with that kind of equipment.

I'm surprised that more LBSs don't ask for test ride customers to sign a contract promising to pay the full cost of the bike if damaged and take a c.c. imprint to confirm this.