Blood glucose is regulated by insulin. When it is too high, the patient will "dump" the excess glucose in the urine. If high glucose levels are found in the urine it could be an indication that other tests need to be done to determine for sure if the patient has diabetes.
High lipid levels often lead to deposits of lipids in blood vessels and these can clog the arteries. A clogged artery in the heart is a heart attack and one in the brain is a stroke. Thus finding out who has high lipid levels is important to prevent those occurances. Drugs and diet can help.
Finally, finding protein in the urine suggests some major kidney problem such as infection or damage from another cause or even high blood pressure - all of which need to be followed up to see if there is some type of underlying disease not described by the patient on the basis of symptoms. Thus the simple measure of getting a blood test for glucose and lipids and a urine test during your annual physical can tell your doctor a lot about diseases you may have that you don't even know you have. Another common test at annual physical time is a blood count to make sure you have enough red cells and hemoglobin for oxygen, platelets for clotting and white cells for fighting infections.