Traditionally all manufacturers have been using a little bit different connectors on the laptop. Also tho voltages seem to differ a little bit. Hard to see any

Traditionally all manufacturers have been using a little bit different connectors on the laptop. Also tho voltages seem to differ a little bit. Hard to see any other real reason for this than to make switching to another brand a little bit harder and to make a few extra $$$ by selling accessories. So even if adding a new USB port for charging is cheap and easy, the manufacturers might still have reasons not to do it.