Answer
If the introns were not excised and, instead, were read as exons, the resulting protein would not be the correct protein coded for by the mRNA had the introns been excised.
Work Step by Step
If the introns were not excised and, instead, were read as exons, the resulting protein would not be the correct protein coded for by the mRNA had the introns been excised. We might end up with a protein with extra amino acids, turning the protein into a different protein than the cell needed to produce.
