I wholly agree with Colin and economyman. It's simply the structure of European airlines' fares, and it has proved to be a fairly profitable way to run the business.

However, I have found bmi staff to be really kind and forgiving. One occasion comes particularly to mind -- this was before I had any status with BD.

Rushing to the airport on Sunday evening for the penultimate EDI shuttle of the day, I was caught in horrible traffic on the M25. I arrived with 15 minutes to spare, but since I was heading back to university, I had bags to check and there was no hope. I went to the ticket desk to see if (and how much) a seat was available on the last flight. Taking pity on me, he put me on standby, free of charge -- I got the last seat on the plane.

Oddly enough, that great service, along with a few other instances, gained bmi revenue by converting me to using them for all my domestic travel (and until now I've been really happy with them).

EDIT: Reflecting on it, there probably is something to be said for the much smaller corporate size of BD compared to BA. I can imagine that the staff at the T1 ticket office are (were?) more empowered to permit 'waivers and favours' than someone at one of BA's myriad desks.