Locking exposure on the 7D

Apples to oranges. A P&S meters off the imaging sensor, and it reads the sensor all the time in live view, so it's easy to link the AF point and the metering area.

A DSLR uses a separate metering sensor, and having a spot meter at each AF point would require a different design of metering sensor. Nikons have metering sensors with more zones, so I bet it's easier to make this work on a Nikon DSLR.

And guess what? If you use your DSLR in Live View, it links the meter to the AF region. I just tried it on my 60D.