As one of the advocates for this on this forum, let me make things clear if I can.

Modeling restraints with the stiffness of support steel is not usually necessary. Pipe racks and building steel is typically many times more rigid than spring cans or hangers, for example. Also, if you find nothing objectionable in your piping system using the assumption of rigid supports, why bother? I (and presumably you, too) get paid to complete projects in as little time as possible consistent with good engineering practice.

When you have pipe with bending stiffness on the order of magnitude of the steel you are attaching to, you may well want to include calculated stiffnesses at your support steel. I have seen pipe racks with 2" of deflection at the center of the span of the member - clearly that is a case where one would want to include the support steel in your model.

I have intentionally left a gray area between cases where it's obvious not to model support stiffness and a case where it's obvious to include it. I cannot and will not force you to accept my engineering judgment - a part of your development as a stress analyst is to understand what portion of this gray area you wish to enter.