Tables get a lot of stress. When people move a table, the common approach is to grab one end and either pull or push the table. This puts a lot of stress on the legs since the bottom of the leg wants to stay in place and the top is being pushed. This requires a strong joint between the leg and the apron. Mortise and tenon is the best (strongest) joint for attaching legs to aprons. Dowels are not as strong as mortise and tenon.
Mike
Go into the world and do well. But more importantly, go into the world and do good.