I think weather might also have something to do with this. As we all know, the wx in the UK is too unreliable to allow visual traffic; too great a risk of deviation to remain VMC and with our already overburdened runways we cannot go wasting capacity to accomodate littluns. (Ask Nick Faldo). Anyway, as ATCO 2 says, providing the ATC staff for that when we haven't got enough for the "payers" just isn't on.
I would guess that at LAX the average wx is reliable enough?