Like vinnie said, the spots where rake matters are very marginal anyway. However there's still an edge in factoring in rake into your decisionmaking.
Following the logic of: most people are able to play correctly in very obvious spots --> your edge comes from marginal spots it makes sense to use rake in your calculations. For most people this is limit to playing different ranges preflop (play a few big pots vs many small pots). I don't know if anyone goes as far as using rake in on the fly calculations since the edge is very small for these situations, where optimal play is ambiguous at best, and very sentistive to assumptions at worst.