If it wasn’t raised on the record in the trial court, it didn’t happen for purposes of appeal. Like every generalization, there are exceptions to that rule. But no appellate lawyer wants to be in the position of having to come within some narrow exception for raising unpreserved error on appeal in order to prevail.
So, it’s critical for trial lawyers (and appellate lawyers who help at trial) to know the rules for preserving the record for appeal. Following these rules has the added advantage of helping you win at trial – after all, the trial judge is more likely to get it right if he or she hears your arguments while the case is still ongoing.