I can understand why
United doesn’t just let people sit in First Class when there are seats

If you want First Class you have to pay, with dollars or miles, to upgrade your seat. 

First Class is truly a
different class of service.

The flight attendants do
more for you. The food is different. The alcoholic drinks are free. The “cabin” is physically separated from the
rest of the plane and it has its own rest room.  

I get all that.

But Economy Plus is
nothing but more room.  

The same flight attendants
serve Economy and Economy plus. The same
food and drink are served (food for purchase, of course). Both classes of seats are in the same cabin
and use the same rest rooms.  

So why, when a plane has a
ton of empty Economy Plus seats, don’t they just let Economy Class passengers
move up to Plus on a first come, first served basis?

Isn’t it an opportunity to
deliver some great customer service? 

Or, perhaps, to initiate an Economy Class passenger to the joys of more leg room (that they might even
choose to pay for next time they fly)?

Why not just let them

Just to be clear, I have
nothing against United Airlines.  

In fact, ever since my
flight status changed, I really like them.

Now they put me in Economy Plus automatically all the time. 

I just wish they’d extend the courtesy to