[rogerbinns]

Several reasons. The biggest is what netmask to use. 192.168.x.x was originally a class C (/24) and the default netmask to use is that resulting in the least number of problems.

With 10.x.x.x, the original was class A (/8) but it is extremely unlikely you want that as the netmask. Other guesses could be wrong.

Additionally because of its size, it is likely used in corporate networks. This would cause grief with vpns if both your local network is 10.x.x.x and the corporate vpn is 10.x.x.x.