Because it looks better to have a smaller joint, if it is cut at a 45 it will be longer.Question: When installing baseboard, crown, etc., why is a scarf joint cut at 22.5 degrees and not 45 degrees? Is there a specific reason for this, or is it more of a local tradition? Does anyone do it at 45?
I like a 45* scarf on base... larger area for a glue bond and better cross nailing (larger overlap). Also the bigger the angle the more edge grain you have for a strong glue joint (22.5* and smaller angles mean you are essentially glueing endgrain to endgrain).Because it looks better to have a smaller joint, if it is cut at a 45 it will be longer.
Homeowners will scarf a joint at 45 because they don't know any better.