Why do Scotland and Wales have more constituencies than England and Northern Ireland?

I think that rather than proportional representation there is a case to be made for having constituencies containing an equal amount of people. At present the system favours like you say scotland and wales but moreover favours labour because labour strongholds constituencies have fewer people on average, which is not fair in the slightest. In other words there are more labour constituencies but not necessarily more labour supporters. The boundary lines should be redrawn.