This bugs me because this is what happens to me:

1. I book a $$$ ticket for work or personal. I'm 1K and get an E+ seat
2. My wife wants to come along
3. I book a miles ticket for her but now we can not sit together unless I sit in E-

One of the most important benefits to me as a 1K: "Economy Plus companions: 8" meaning I can book 8 general members into E+ but we need to be on the same ticket, which means I need to pay ($$$) for my wife's ticket now... so what's the point of miles?