I work at a shop that sells and repairs bikes and we get everything from high end road bikes to Wal-Mart specials. All the bikes I see with nuts on the axles have 3/8x26 on the rear, regardless of whether they are single speed or multi-speed internal and 3/8x24 nuts on the front axles. It's just a fact of life that some things on bicycles have to be weird especially when although they're 3/8 inch fasteners you use a 15mm wrench. And another thing that amuses me is when my co-workers tell customers that presta valves are superior to schrader valves even though presta valves are on nothing else in the universe but bicycle tires. $100,000 cars and $200,000,000 airliners use good old schrader valves. And aircraft use schrader valves not only one the tires but the landing gear struts which can be subject to thousands of pounds of pressure.