The problem is that many PCB packages started off life in the days of MS-DOS before there were the established UI conventions of Windows, and where memory, CPU power and disk space were expensive. Most supppliers had to invent their own UI, and often design it around the limitations of the system to get acceptable performance. (I gather much of ORCAD MS-DOS was done in assembler - it was certaonly very fast in comparison to other tools of its time)
Once the Windows UI and more power came along, the CAD suppliers didn't want to upset their existing users and incur large development costs to change thinsg radically, so they kept the UI similar whilst adding Windows functionality.
Some packages also have baggage from the days when PCs weren't up to the task, and CAD was done on an assortment of very expensive workstations under different operating envirionments.
There are a few other reasons some tools are peculiar, in particular CAM type tools tend to be oriented towards the devices they will eventually output to, so for example one convention is that instead of selectin an object and doing something to it, you first select a tool, then apply that tool to one or more objects.
Many years ago I evaluated several PCB tools, and went with Accel (which became P-Cad before Altium abandoned it in 2006) primarily because it was very obviously designed from scratch as a Windows application with standard UI conventions, and had no UI baggage from earlier tools. It's a tool you can pick up easily and be using productively in a day or so.