Lots of reason. We are talking about a port moving 40 gbp/sec of data. This is not like moving data an USB2 port. Signal conditioning etc issues. As AceFernalld points you likely need another controller because of the distance.
But, is it really that inconvenient to have the ports all on one side. I don't remember people gnashing their teeth because there was a magsafe connector on only one side. Or OMG the two mini display ports were BOTH on one side. And only one HDMI port!
Seems that having any of these on the "wrong" side ports can be remedied by buying a 1/2 meter longer cable, just like you did with the old rMbp.