You often get an instruction like "use the left 2 lanes". But where you are when the instruction is given, the leftmost lane might be a forced early left turn. If you're unfamiliar with the location, this requires a lot of extra cognitive load, vs simply not giving that specificity at all.

As well, traffic conditions change rapidly and the lane by lane doesn't account for that.

In some easier situations, it's great, but it's a negative in more complex situations.